cecillia I had a molar pregnancy between dd1 and my 2nd child. Like you, I was absolutely devastated, even though I already had a baby, and was convinced I would never conceive again. In my case it wasn't diagnosed till I was 15 weeks pregnant, and we'd told lots of people I was having a baby. in some ways this made it worse, as we had to tell them, actually, we weren't now having a baby, but in other ways it helped, as lots of people came out with their own stories of pregnancy disasters there's an awful lot of it out there, I discovered, but generally not talked about.
The follow-up is a nuisance, but no more than that -- it involves sending off little test-tubes of wee in the post, and having the occasional blood test. My hormone levels took longer than usual to go back to normal, so I was followed up for a longer period. The people at the follow-up centres (Charing cross hospital for south of england, sheffield for north, Dundee for Scotland) are great, and will explain things endlessly over the phone if necessary.
In fact I got pregnant before the end of my follow-up time (NOT recommended, but it is v. hard to use contraception effectively when you're desperate for a baby) and he was fine, as was my dd2 who was born a year ago. I've had no related health problems since, and no problems with either subsequent pregnancy. You should be offered an early scan (6-7 weeks) in subsequent pregnancies, to make sure all is as it should be.
I do understand how you feel at the moment, but the chances are very high that it is a one-off, and that you will go on to have a normal pregnancy.
hth -- do feel free to CAT me if you want more info.