PCOS, letrozole, TTC, cramping, help!!

Need some help!

We have been ttc for 3 months now and with a crazy cycle thanks to PCOS it’s been difficult.

I had a period no period for over a year and a half but finally got one beginning of August 2017,

September- nothing

October- period at end of the month

November- end of the month

December- nothing

I went to my obgyn and he suggested letrozole which I started beginning of January for 5 days. I have to take it again when I have my period.

But last weekend I had really bad cramps and last Wednesday I had a tiny spot in my underwear and when I wiped...I thought oh good my period now I can get back on track BUT that was it ! Just that tiny bit of blood.

Thought maybe it could be implantation bleeding but I’ve taken a bunch of test and all BFN

Ughhhhh any advice??

I had horrible diarrhea last night and now cramping tonight.

Help!