Am I Pregnant?

I don't know the answer to that question. We weren't trying (and in fact weren't planning on having anymore children).  We use birth control. The only problem is I am five days late and sore in spots I only get sore when I'm pregnant. My major worry is that if I somehow got pregnant, it was during the time I was taking an antibiotic you are not supposed to take when you are pregnant because it causes birth defects. That really scares me.  I'm not nauseous all the time like I am when I am pregnant but I have been nauseous a few times for no reason and it is early yet "if" I am pregnant.  Though, I've not needed the best acne cream like I usually do when I should be starting...oh boy.  Where are the signs of a pending menstrual cycle? 

Oh where, oh where, has my period gone, oh where, oh where can it be? 

Between my thyroid disease and pelvic inflammatory disease, and history of having a very hard time getting pregnant (like 18 months of trying to conceive for our last little one), if I am pregnant, it would have to be some very dedicated swimmers and egg because the chances of me getting pregnant should be slim. 

I've avoided buying a pregnancy test so far.  I'm trying to hold out until I am a week late and then see how I feel.