No period for 3 months, not pregnant?

[Kennyblake]

First off I'm not trying to conceive, I have been on two forms of birth control (Nexplanon implant then birth control pills) since May of last year but quit may this year due ton not being able to handle the side effects. I decided to try charting because condoms and sponges give me back UTIS, but I had to wait for my cycle to start back from the birth control. I had a light period immediately quitting the birth control in may, but missed it in June. The last week of June I took plan b after using a sponge but having to take it out early due to it being too uncomfortable. I had a very heavy period the next week on July 4 and haven't had a period since. Throughout these past 3 months I've moved and started college and a new job, and battled a bad UTI with antibiotics and just finished up a big cold. I have been taking pregnancy tests ever 2 weeks, and just took another yesterday, and they are all negative. I feel fine, no symptoms of pregnancy or an infection. In August I had light spotting just when I wipe fir two days and had a little more in September but not even enough to wear a liner. Lastly, I have started having some bleeding after sex that just started happening the past week. It doesn't even last a day, just when I use the bathroom right after then it's gone. Could the spotting the last few months have been some form of my period? When should I start to worry? Just looking for some opinions and input on what's going on, thanks so much.