Hallow Dear, Both the pills you have mentioned are birth control pills. Lo Loesterin Fe is a low oestrogen pill hence it may cause low bleeding. Tri-Sprintec is a average Oestrogen-Progesterone pill. If you were on one brand pill regularly and just change the brand without having any gap, the chances of protection are very high. Moreover, the intercourse happened in the first week of menses. This is little away from the fertile period. Egg release in women happens 14 days prior to next menses. Considering 24 hours life of egg and 72 hours activity of sperms, a week around this day is considered as fertile period. Already on birth control pills and intercourse away from the fertile period, the chances of pregnancy are very low. You have not mentioned whether you have missed period or not. Missing a period is the first and cardinal symptom of pregnancy. All other symptoms appear later. Your breast and nipples symptoms could be due to rough handling also. Still if you are in doubt, please wait for the periods to miss. If at all it misses, then 8-10 days after that perform urine pregnancy test and/or ultrasonography for detection of pregnancy; done earlier, they may prove to be inconclusive. Beta hCG tests are conclusive even 2-3 days after missed period. I hope you are satisfied with the explanation.