NEVER hold your pee, especially right after sex. i don't think this is a sign you're pregnant (not that i'm saying you couldn't be, just that these symptoms are most likely a urinary tract infection.) you should go to the doctor and get a urine test done, but they will most likely tell you it is a UTI, and give you antibiotics. if you absolutely cannot make it to the dr., you can drink cranberry juice and pick up some over the counter medication called "cystex" in the feminine health aisle of some drugstores. the azo and uristat brands never work for me. they do not have the antimicrobial in them that cystex does.
also, i'm not sure if a pregnancy test will be accurate this soon after unprotected sex. if you have a sensitivity to latex, please at least use the SKYN ones. they are made for people with latex allergies.
for future reference:
1. USE PROTECTION (i would tend to avoid spermicidal condoms as some people have sensitivity to them)
2. go to the bathroom and pee or at least wash/rinse down there immediately after sex to avoid bacteria getting into your urethra
3. while you have a urinary tact infection, it is fairly common to pee some blood (if it's a bad one). do see a dr if at all possible, but try not to freak out too much
4. drink plenty of water
5. try to wear breathable clothing (cotton panties as opposed to satin) and nothing too tight while you have a uti
6. try to cut back your sugar and caffeine intake while you have a uti
7. make sure to wash down there at least a couple of times a day. sometimes harsh soaps can make it worse though, so be careful not to use anything too harsh. i actually DO use anti-bacterial soap down there right after sex just to avoid uti's, but that is risky because anti-bacterial soap can cause yeast infections.
many years of dealing with them