Starting Clomid Next Cycle! I need some help please

Hello everyone. I went to my doctor yesterday because I’ve skipped a period for the third or fourth time since 2019 has started which is odd for me because I am sometimes late but I never miss a period unless I was pregnant (I have a 2 year old and a angel baby).

He had put me on progesterone in June since I missed Mays period and I got my period, we baby danced, I missed my period(for the fourth time this year), tested...and again no period but no positive test.

I am about 15 days late now so when I told him this he prescribed Clomid and prenatal. However I still haven’t gotten my period and i can’t start it without my period...he didn’t prescribed me progesterone again so I was wondering if it would be safe to just buy progesterone myself, take it for ten days and wait for my period?

Also he put me on Clomid for six months and said if I don’t get pregnant then they’ll do further testing...isn’t that a lil backwards? Shouldn’t they test for PCOS or something first then prescribe clomid?