2 misccariages. I was not pregnant!

I am 33 years old. I had my period on 28 February. My cycle is regular and of 28 days. I started getting very light bleeding/ spotting from 28 March. I checked urine at home on 7th April which was positive and on 8th got beta hcg test done which was133 miu/l and sonography didn't show anything except thickened endometrium 13.2mm. On 11 I started bleeding with severe cramps till 16. I passed some large cloths as well. On 14th I repeated beta hcg which came down to 20 and tvs didn't show anything except thickened endometrium 11.1mm. Now I have got sonography done on 15 which shows endometrium thickness of 3.1 mm. My doctor said it was delayed period. However in Aug 2016, I got positive urine test on 10 while my last period was on 2July. I took some adventurous ride on 8th Aug. From 13 August I started bleeding which stopped on 19 August. My doctor didn't do any D&C or sonography or beta hcg but gave medicine. The current doctor told me in both the cases I was not pregnant