yellow discharge, all test negative

I've been experiencing water-like yellow discharge for a few months and bleeding in between periods, I went to the dokter to get tested. STD test's came back negative so did the test for bacterial infection and yeast infection, the dokter send me to a gyn she did multiple tests all which were negative the pap smear was normal too. she did see a thickened uterine lining on the ultrasound so I was prescribed provera for 10 days, I got a normal period 7 days after. then on the 1st of juli I was fooling around with my ex-boyfriend he tried to get in me, but I pushed him off because I didn't wanted it (it was unprotected)
Then I had a hysteroscopy on thirsday the 8th everything looked normal. on the 17th I got what should be my period but it was like half the bleeding I usually have so I have been freaking out for quite some days now, today I did a pregnancy test again and it was still negative (can I possibly be pregnant?)
or can provera causes a lighter menstuation a month after using it?