1) it hurts when you pee
2) you see puss, sores or blisters
3) you want to suggest BBFS from a partner who is dumb enough to think a snapshot in time makes you safe.

 
cheapest place is usually your local government health agency. Usually less than $100 for the full line of testing. Planned parenthood is also good but can be a few hundred. I prefer to testing with as little paper trail as possible so no health insurance and pay cash.

I'd recommend Planned Parenthood or your local health clinic the most for privacy's sake. I know a lot of people have family doctors etc and the subject of why you're getting tested if you "supposedly" only have one partner can get icky. But regardless of where you get tested, I'd recommend getting tested at least every 6 weeks. Keep in mind that sometimes STIs don't come up on panels immediately and so frequent testing with a set schedule is absolutely recommended.  
Be open to the clinician that you're having "pretty regular sex with multiple partners". You don't have to say with who/in what context but tell them that you're having a lot of sex and go through the checklist of the full panel test including HIV.  
But regardless of the kind of sex you're having (bare or covered), get tested. Recommended (I believe) is to get tested until at least 3 - 6 months from the last time you've had a new sexual partner.

If you play it safe what ate you testing for?

Google std test and you will find a company that uses Quest labs which are all over. Totally private.no paper trail. Prices listed about $200 for panel of most common $100 more for Tric. Results online and quick. If a positive test a Dr will provide a prescription (for additional fee)

My primary care doctor gives me a free one every year and I use BC/BS insurance. I’ve gone to the doc in the box type place if my primary care doctor is closed and they charge a co-pay. I go regularly.

I use this: https://www.mylabbox.com/product/total-box/

I get tested once a month, assuming I saw someone that month who I wasn't in a monogamous relationship with.

 
The cost is probably subsidized somehow, and I use my HSA to cover it, so it's not anything out of pocket for me. This is probably a no-go for most guys here, because your spouse could intercept the package. Not everyone has such vices.

I play safe, but testing seems prudent. There are lab franchises that welcome walk-in customers. I go once or twice a year on a week day when it's not busy, fill out the paperwork with an anonymous name and pay cash.  No paper trail, easy, and the sense of ease from the negative results help me relax and enjoy. Any positive result and I quit P4P immediately.  

My doc has me on some meds that have the capacity to play hob with my renal function, so we do a blood draw and tests every 6 months. While the blood is already in process, I have them tack on the STI test panel. Doc knows I'm a sexually active adult, so he's just happy that I'm being responsible as a matter of course.

Always wanted to do it.  Always thought my life was to valuable to risk ever jumping out of a perfectly good aircraft.

Man, you guys are sponsoring the industry!

I typically get tested twice a year, which is twice as often as the people of the sexual health department recommend for visitors of prostitutes (legal here you see). When I tell them the number of visits, number of girls and sometimes lack of safety (BBBJ in almost 100% of the cases for instance) they agree it might be better to go twice.

Up til a couple of years ago it was free for any John, but they changed that because there were too few actual STDs to warrant the costs; the girls still can get tested for free (these rules are by law and set for the whole country). As a service to Johns, once in a while they have a STD test bus set up in one of the red light districts and anyone get tested for free. They actually have people walking around and asking men to have a go. Even though I never go to any of the girls in the RLD, I will make use of the bus if I have the time. Actually kind of fun to hang out with the "nurses" and other guys while waiting your turn. Given my frequency of girls, I've also been told to just give them a ring if I wanted to get tested (despite the law change).

All of this anonymous and free; if you have symptoms you will always will be able to get tested and get treatment for free (if it's the clap or chlamydia, they have doctors in the mornings that do the culture while you wait).

The necessary test are determined by the medical professionals and typically consist of nor more than:
-Chlamydia
-Gonorrhea
- HIV
- Syffilis
-Hepatitis B

About once a qtr  

That seems to make sense. I don't have to tell the doc I'm banging hookers, just that I'm sexually active and proactive about my health.

I get tested every month, full panel, covered by insurance

I live in NYC so the clinicians just think I’m responsible

¯\_(ツ)_/¯

Being on PrEP (HIV prevention medication- a simple step I take to ensure safety in case of breakage, etc.) necessitates a lot of blood work, so I just go ahead and get full panel tests done whenever I need to go in for that. My local Planned Parenthood is awesome, accepting, and totally SW positive. Highly agreed with everyone saying staying in the know is far better than waiting until symptoms arise, especially as so many people can be asymptomatic but still positive for an STI.

22% of clients said they'd never been tested. utterly appalling imo.

...i used to do benefit concerts/fundraisers for the free clinic in the city i live...in return...i can get full,complete STD check-up 4 times a yr or whenever i need it ...been "FREE AND CLEAR" since 1985...i love the taste of a hot wet pussy-its why i do regular checks...gang...if you do uncovered oral sucking or licking...get a seasonal check-up...check your towns free clinic...if you have one...