Just in desperate need of advice 😩 someone please help 😭

Before i was on BC my cycles were normal. I had a regular 26-28 day cycle. I got on BC when i was 17 and was on it for a year. Then I got back on it December 2016 because me & my boyfriend at the time had a pregnancy scare (well he was really the one scared). So i got back on it and then i got off it in May 2017 because i just wanted to give my body a break. When i first got off BC AF would sometimes come like 3 days late and then i realized that my Cycle has suddenly switched to a 29-31 day cycle. Which was unusual because i always had a 26-28 day cycle. But i didnt think anything of it because i thought it was because of me stopping BC and my body trying to be back into the rhythm of things, you know? But boy was I mistaken. My periods were regular from June 2017 - January 2018. January 12, 2018 was the day of my last “regular ” cycle. My cycle for February was due on the 11 & At first i was excited when my period didn’t come for a week.. i thought that finally after 8months of trying, i was finally pregnant and i could finally surprise my fiancé with a onsey and a positive hpt or something sappy and cute like that.. so i took a test and just knew it would be positive. I was wrong.. not even a faint line. I was confused & my heart was broken.. i went to the doctor and their test was negative too. They told me not to worry about it and that i could just be changing cycle. So i waited and AF finally showed on February 25th. After that, i got some weird brown discharge on CD 17-19 which would’ve been the middle of my cycle. I was kind of confused but i just went on with my day. Now, my period was supposed to come on March 26th and I’m going through the same sitiation as last month. I’m currently 10 days late and BFN. I have a doctors appointment on Thursday cuz it’s becoming a cause for concern and I’m getting nervous and starting to think i can’t have kids.. mainly because I’ve been having unprotected sex for 10 months and nothing has happened and now this is happening... so have anyone experienced a similar situation?? What was your outcome? Any advice?