Two years ago I had two m/c's (one m/c then a period then another m/c!) and so I am really worried about having sex and think bad things for the rest of the day/night due to the worry that I am going to m/c again! Both my last m/c's were sex related,
Although I'm not a Doctor, I do not believe sex is usually the cause of M/C's. Although I believe in some cases sex can help aggravate a situation, I suspect more times than not it is a case of coincidence. That being said, your feelings and concern are very real and consistent with my wife's and every other woman I know who has ever had a M/C. In that regard I would not worry about it, its a natural feeling to go through. I also suspect that no matter how bad you don't want to feel that way or make your DH/DP to go through this, you are not going to be able to change how you are feeling.

My wife seems to be almost as prone to M/C as she is PG's. We do not seem to have a problem conceiving, she is very fertile but we usually have at least one M/C between PG's it seems; The worst being a loss 3 months into the PG. My wife was so impacted by our first M/C that she did not want me to know how bad/constantly she wanted sex for fear we would have sex and cause another M/C. I found out years later! However, having a successful PG did not change her fears and added to a decreased drive has meant we just don't have allot of sex during PG. With my son (our last PG to date) she had a little more drive but not much and the same fear was there. I don't think any woman who has had even one M/C let alone multiples can go through a PG without that feeling riding on her shoulders.

I would recommend talking to your DH/DP and laying out your fears while also explaining your concerns for his needs as well and see what the two of you come up with. If both of you are on the same page desiring this baby more than anything, then I am sure the two of you can come up with some sort of understanding that the two of you can live with for the greater good of everyone and everyones emotional state.

Good luck!