Stressed because of miscarriage.

Hi! I was pregnant for 3 months.had a scan at week 7 growth was 6 weeks 4 days flickering noted, then brown discharge at week 11 had scan no heartbeat no growth, was only 7 weeks, miscarriage happened. I was dreaming about the baby and I couldn't accept this, now it has been a month and am trying to move out of this but I want to make sure that this will not happen to me again. I have taken thyroid test before abortion TSH was 5.6,i checked it should be 2.5 while pregnant, this maybe the reason? then I took apla suggested by another doctor that is negative. Am 27 now,few are telling take 6 months gap my doctor told 2 months. Am worrying lot the age is going this was my first pregnancy and I lost. I used to get periods within 35 days max. Am 45 kg ryt now height 5 inch my husband weight 80 height 5.4 inch. Please suggest tests? Should I need to wait for 6 months to get pregnant? Or can I plan after 2-3 months? Pls guide how to avoid miscarriage? The word "no heartbeat".Thanks much!