No period for 3 months after Plan B?

So up until February of this year i had the Nexplanon implant, that completely stopped my period, taken out and started the pill in April, but stopped the pills in May due to a bad reaction and immediately got my period in late May. I never got my period in June, negative pregnancy tests, and had to take Plan B in late June due to having to take a contraceptive sponge out too soon and wanting to be safe, not sorry. However, being my paranoid self, i took another Plan B after a condom breaking just a week later. I got a very heavy period just a few days later on July 4th and haven't had one since. Im having no symptoms of pregnancy or infection and  have been taking pregnancy tests every two weeks just to make sure, all have come out negative. I had cramping and spotting like my period was about to come for a couple days in August and then about 4 or 5 days in September, but it never full on comes. Its now about 3 months with no period and no sign of it coming. Oh, and stress wise, i have just recently moved, started a new job, and college so i have a lot on my plate lately including being pretty sick twice with a UTI and cold. Has anyone else experienced this? Just looking for some advice, if i should just be safe and wait it out, or when i need to find a doctor.