I had intercourse with my boyfriend on January 7th, just three days after my period. I am supposed to start ovulating tomorrow. Would I have to have sex again in order to get pregnant, or are my chances just as high with only having sex once? I have blood work on Tuesday of next week, would that detect a pregnancy after 8 days? I have also been experiencing lower back pain, lower stomach pain, really horrid headaches, sore breasts/nipples, and my pee is as strong smelling as ever. I know it's possible to overlook symptoms and have your mind play tricks on you, but I haven't looked at any. So basically is it too early for me to be pregnant? My period is supposed to start on the 28th, so waiting until a missed period isn't really an option. :/

There are no signs at a few days, seldom signs at a few weeks. Most signs don't start happening till 2nd month, so yes mind playing tricks.

If you are properly tracking ovulation ( not using those silly online or phone tracking) then sex 2 or 3 days before. Which is the day the temp goes up, temp goes up normally about 2 days prior.