Should I not do another round ?

I did 2 rounds of clomid and on my last round I got pregnant but it ended in a chemical. When my period came it only last 2 days which is very strange for me because my periods are usually heavy and last about 5 days. Is it possible the clomid is thinning my uterine lining? I’m suppose to start my 3rd round today. My doctor said that usually doesn’t happen and “ I’m sure it’s fine “