Anything is possible, even in th Hobby world!
my entire life change, after I find out the my husband had an affair for more than two years. I still have a feeling that he is cheating on me but I have done everything that I can do to catch him, but I still can not prove him nothing. Everytime, we together I have notice something different on him. I really don't know how to ask this question. It has to do with our intimasy time.
Polygamy is natural.
Monogamy is a noble man made aspiration.
There are a couple of VERY common, BIG reasons for marital infidelity. There are also a myriad of others lesser ones.
Does your husband still love you? Does he still communicate and share with you regularly? Does he provide for your needs both material and emotional?
Sex is a very enjoyable physical sport that secondarily feeds the ego.
Intimacy goes far beyond sex. It gives safe haven for ego and was/is a huge underlying reason for marriage.
You can purchase sex
You cannot purchase intimacy.
If you are giving your husband sex regularly then one of the most common reasons for male infidelity can be ruled out.
If you are still "intimate" then you are still probably No.1
If you are his best friend, confidant, partner and champion; some patient rooting through the "myriad" of other “lesser” reasons for his infidelity may supply the formula for you to regain the position of No.'ONLY'
Sometimes their husbands even have to hire providers for sex... Providers are tired at the end of the day 
for many smittened hobbyists wanting to turn their ATF into a GF or SO.
Anything is possible, even in th Hobby world!
So that is why you are so tired when i get home every day
Thank You
But only 1/100000 is married 100% of the time. lol
Did you come to TER just because your hobbyist husband was cheating on you or are you involved in the hobby somehow?
Asking this on The Erotic Highway link on the left side of this page may be more helpful as there is a woman there who is a licensed therapist.
My advice (consider who it's coming from) is to stop trying to catch him and instead try to spice up your love life and be very intimate, look sexy, and have lots of wild sex as often as you can. Think about why a guy would cheat on his wife and go from there.