My period is late, & I have a 4 month old.

I started these weight loss pills, like couple weeks ago. Hyrdoxycut I believe it spelled, & I am late on my period. I took like 5 pregnancy tests and they are all negative.... The condom broke like a month or so ago with my SO BUT I took plan B right away like an hour later, if that. What do I do?... PS I just recently took another pregnancy tests & it's still negative right away. Since than no condoms have broke or anything.