Am I pregnant? Or just irregular? HELP

Hi. This is my first time to post here so here it goes.

My period is kinda weird and I have no way to track it because it comes very irregularly.

For example last year: one month I have my period and it's very light to moderate and I barely have cramps. Then It lasts for 3-4 days. Then come next month, I don't have my period but I am not sexually active.

The following month I have my period and it feels as if all of my blood is being drained out of my body, accompanied by cramps. And it lasts for 3-5 days.

But this few months have been giving me quite a scare. I am now sexually active, and I still haven't gotten my period though I got my last period on Dec 2018. I recently had light "bloodshed" that would come and go every few days or so and what's strange is that if I do not have any napkins, it would flow like crazy but when I do, it just STOPS.

My discharge is crazy too, I feel it flowing out and it makes me run to the bathroom to check if I got my period but I always end up disappoint and more anxious. My boyfriend and I use the withdrawal method so I am scared that I might be pregnant.

Has anyone had these same symptoms?

(Sorry for the long post hehe.)