Do the Pills Trick You Body Into Thinking Your Pregnant?

Ok, im very paranoid about being pregnant all the time. Im on birth control pills (ortho tri cyclen lo), and take them every day same time, to my knowledge. The last time I had sex was sept.6, and we used a spermicidal lubricated condom (my fiance' also has a rare case of pituitary/thyroid disease, where his Dr. Is pretty sure he cant have kids without meds.).

Ok, so the last time we had intercouse was sept. 6, then I got my period sept. 22 (on time). In oct. We "fooled" around (i.E. Dry humping, but one of us always had underwear on, etc.), I was on antibiotics for a few days this month, so I was worried (again), about being preg. So when I went to the drs. Oct.21 I got a blood preg test done = neg. (got my period oct. 20...On time). Then when I went back to the drs. (other med reasons), she took another blood preg test (nov.17, same day got my period; on time), came back neg.

Last monday (2nd day of new pack), I dropped my pill, and (this is why im on meds and see a therapist), flipped out, but then I found it, put it in my mouth, looked in a mirror and saw it on there (afraid that I didnt take it though), on that friday my fiance' and I had oral sex.

This week however (2nd week of pills), my breast are a little bit larger, and sometimes they hurt (but im sure its from pushing/poking them). Im scared that I might be pregnant (esp. If I didnt take that pill last week like I thought). However, we haven't had intercourse since the beginning of sept.

Is it normal for your breast to get bigger during your cycle? They usually become sore and swollen about 10 days before my period, but its over 2wks till im due again. Is this just the pills tricking my body into thinking its preg? If I weren't on the pill, this would be around the time I would be ovulating.

Any advice???

* started paxil cr last week, so im thinking my hormones are messed up or im retaining fluid *