Phentermine = Missed Period ??

I started taking phentermine almost a month ago. I had a period in the middle of it (because I have two periods a month and we can’t figure out why). I started another period (or so I thought) about 5 days ago. It was just some brown mucous discharge which is typically normal for the start of my periods. I realize today that I haven’t actually bled one time and that it’s just darker/cloudy mucous IF I have any. I also am experiencing severe back pain and headaches. Back and hip pain are not normal for me in the slightest.

I guess what I’m asking is: has anyone gotten pregnant while taking phentermine; or did phentermine just lighten your periods?

TIA!