Was wondering in general how safe condoms are in terms of durability?  

What if you are having intercourse with a woman and notice afterwards a drop or two of blood on the cover, but notice no hole or tear on the condom.  

Dear not secure,

Your questions are answered on the linked site. Very good information and lots of it, with decent citations. A sample:

"In the United States, most studies of breakage caused by fault in the condom itself have shown breakage rate is less than 2 condoms out of every 100 condoms. Studies also indicate that condoms slip off the penis in about 1-5% of acts of vaginal intercourse and slip down (but not off) about 3-13% of the time."

Seek and ye shall find,
the Love Goddess

A piece of trivia
a colloquialism in British English for a condom is a "Durex", like in American English a "Frigidaire" is a refrigerator, the brand becoming the generic designator.
An other British colloquialism for condom is "Mac", derived from MacIntosh which is a brand (and the inventor of) the truly waterproof raincoat (oiled canvas, originally)

I had a recent experience, and this happened once before with a gf, where the lady I was with wasn't supposed to meet aunt flo for about a week, but from her playing rough cowgirl, it started then.  I mean I was literally covered with blood when she got up.  Can you actually hit something in there to cause a period to start early?  Everything was fine during oral and brief mish.

It Happens!!!  (That's preferable to the times when a GF was Late!!! as an example!!)

with me, i've noticed that if i have intercourse, especially of the "intense" variety, anytime within the week prior to the normal start of my cycle, it will jumpstart my period. although it doesn't usually happen during the sexual act, more like an hour or so later.

More likely to have rough sex and caused tearing and  hemorrhage, Not "aunt flo".