Pregnant issue. Thyroxine 50mg for 1yr.

My Last period came on 12-June-2019. The day before and on the day I ovulated I and my partner TTC (stands for trying-to-conceive). I am 15 DPO Since, 3 days it spotting started off with brown white mix then turn into pink when I wipe with tissue and today morning then turned into bright red like period but it don't even fill up a pad and one week my temperature keeps rising on and off and sometime I am having vomiting sensation, feeling very tired, also have lower back pain and little cramping but it comes and goes, nothing like a regular period cramp (I don’t know exactly) and I feel like having pregnancy symptoms. My suspicions were confirmed when my period never came on the day my period was due. I took a home pregnancy test and got a negative and again I tested 2 days later it was still negative. When should I take test and what is the problem. Medications: I am taking Metformin and FolyGel for 1and 1/2 month, Thyroxine 50mg for 1yr.