OP I'm very sorry to hear about your fertility problems and losses.
I agree people should be more sensitive, but I also think it's unrealistic to expect them not to mention their pregnancy in your company. Maybe some are not aware of your situation?
Pregnancy can be a tough, scary, exhausting experience. I have HG and although I'm very very grateful to be pregnant (history of endometriosis and ruptured cysts) I find pregnancy difficult and isolating. I've been signed off sick for months, lost touch with many friends, been through ups and downs with DH as a result of feeling so ill.
When we were TTC, my best friend got pregnant accidentally. She had a difficult pregnancy due to SPD she was in a lot of pain, on crutches, unable to get out much. I felt very jealous of her pregnancy at the time, but tried to put these feelings aside and supported her through it as best I could. She is now a lifeline to me during my pregnancy, especially when I was in hospital.
When people moan they are often just trying to get things off their chest, or asking for a bit of empathy or emotional support. Constant vomiting, back-pain, unrelenting heartburn, migraines... it gets you down and you reach out to others to offer a kind word now and then. When you're suffering you often forget other people's problems and being in pain or constant discomfort can make anyone less sensitive.
Maybe gently remind people that you find it painful when they moan about their pregnancy problems. But try and offer a kind word too, if you can. They will appreciate it and be more supportive of you when you need them.