What Causes Abdominal Pressure And Discomfort After A Miscarriage?

I had a miscarriage in January of 2015. I have had two healthy pregnancies, but my youngest is 13. So getting pregnant after so many years i was thrilled. But i never tried until 2015, since my last child was born in 2002. I m 33 and after the miscarriage I ve had the same pressure on my left side and like air bubbles and discomfort that I had when I was pregnant. The whole time I was pregnant I was afraid to urinate because I felt as though the baby was going to fall out. And there is more air and pressure several days after intercourse but gets a little better after a month or so but still happens. I ve tried to get pregnant again since April of 2015 with no luck. Any ideas why this is happeneing? (The air and pressure) My OBGYN brushes it off as nothing. But I know some this is wrong.