Haven't had my period in a while

Hey,

I had my last period on the 15th of August and was super worried that I was pregnant. (I always use a condom during sex. We are very careful but I'm not on birth control)

I did a test and it came back negative but I'm wondering how to induce a period, or if someone has experienced missing their period for this long.

For context: I am in university and very stressed at the moment. This doesn't help and is adding to the stress.

Thank you