Hi, I Had My Baby Boy Via C-section In November!

Hi, I had my baby boy via c-section in November! I have had one period since! I’m not regular anyway and have never been! I am suffering with post natal depression and I’m on citrapolam 20mg which was increased to 20 few weeks ago! Me and my husband had sex in feb and the condom broke, next day too morning after pill! Still no period! I have done 9 pregnancy tests and all negative! I sit up most nights worrying about being pregnant but I don’t have any symptoms! Last few days have been feeling a bit more lightheaded but think that’s to lack of sleep! I had a really bad pregnancy with my little boy! Every time I’ve spoken to my doctor, they have said I would of had one positive test! I’m so worried incase they are wrong! Please advise