Oh Popsy that is so cute about rubbing your tummy it made me want to cry. I kept poking my boobs during the first trimester and saying 'yes, still sore!' I always found it a relief to feel terrible, which I did - awful in fact (cos its twins) - until 11 weeks when suddenly I felt better (therefore making me think it was the end)
I also had the urge to go for private scans or get a doppler but in the end I didn't cos I am too tight and I suppose I didn't want to know if it was bad news. I was also scared that sex was bad so if it makes you feel better to abstain then I am sure your marriage will survive! I felt really horny though so I went for it but then always felt guilty afterwards thinking I might have done something to hurt the babies!
The thing with a twin PG is all the books say "sex is safe in a low-risk pregnancy" but twins is a high-risk pregnancy and they don't tell you what to do then! They also say you may want to abstain if you have a "history of MC" - but what's a "history" - is it one, two MCs? If you have had one MC you don't want that to turn into "a history"! MW always said sex was OK though, evidently it was. If you are gentle the beans like it!
Yes, I think I felt movement early because it was twins. I think 18 weeks is normal in a slim-ish woman with her first baby (a bit later if you are bigger). I didn't feel constant movement till 17 weeks. Before that it was intermittent although DH did feel kicks at 17 weeks if he waited long enough with his hand on my tum!