Spotting 2 days after , on birth control, have terrible cold?

Okay so, I just had unprotected with my boyfriend for the first time on Saturday night/Sunday morning. I had just finished my period about 3 days earlier and am on birth control and have been for 6 months. Im obsessive about taking it at the same time every single day - straight up OCD about taking it. However, with the type of birth control Im on and with my very very stressful lifestyle, I have had little to no periods those months - not worried cuz I wasnt having . Then this month I get a little heavier bleeding on the placebo pill days Now, its two days later after we had and I have some bleeding - not brown, but red. And not alot just when I wipe mostly. Im paranoid that I did something wrong and now I am pregnant. That having a really bad cold lessened the effectiveness of the pill - i was not on antibodics either. Am I worrying too much, and could this just be breakthrough bleeding that my body never got a chance to experience since I have been so stressed?? PLEASE HELP!!