Sex in 2nd trimester.

Has anyone else felt disappointed with sex during the 2nd trimester? My husband and I have a very healthy sex life. I love sex with him usually. Lately I feel like I m having more trouble having an orgasm, getting into a good position etc. I get depressed and sad afterwards and sometimes cry. I feel it could be my belly getting bigger and just not being as comfortable. I get extremely horny and excited so that's not it. I feel sex should be more with the increased blood flow, being wetter and having this connection with husband. I'm 18 weeks and this will be our 3rd baby. I also older this time around. 11 year old son, 4 year old daughter and I'm 30 years old. Any opinions or any other ladies having g this problem? I also have trouble even if.i try to do it MYSELF !! What's is happening to me. Will if get better or is this my new sex life? Dull and boring?