Confused and hurting

The following is not something im proud of but its tearing me apart. Im confused, have a constant empty feeling inside and have no appetite.

I have been in a relationship for 6 years of which we are married just under a year. At the beginning of our relationship "honeymoon period", sex was often and great and we were very intimate. For the past few years however, it doesnt happen often at all (maybe once/twice a month) and I always end up feeling disappointed as its always the same unexciting routine and position, and she never initiates it. As a couple we show little affection, but not nearly as much as we used to, whilst friends/couples around us are much more so. We dont cuddle up in bed or kiss much in public. Things that I used to do such as kiss her on the neck, she now finds "ticklish" and doesnt like it. Apart from this we still get on great and have lots to talk about and can have a laugh, however im just finding there's something missing. The following hasnt helped and is why I have started having these thoughts

For about a year I have been emailing and chatting to another female at my work. It all started off very innocent. We get on so well, and it feels like how things were when i was younger and single (i know im not). Nothing has ever happened between us until recently after a night out with some mutual friends, we ended up sleeping together. Since then I cant stop thinking about her. It was like things were back when i first met my wife. Sex was exciting, we cuddled in bed and were affectionate. This is now tearing me up inside. I still love my wife. I dont want to throw everything away that we have worked so hard for, and to make matters more confusing, she has just told me she is pregnant. I am of course happy about this as we had planned it (most our recent sexual encounters have been for this sole purpose).

I know that what i feel for this other person isn't really love (although it feels like it), however I cant stop thinking about her and how it felt spending the night together.

My wife doesnt know about this

My wife will often ask me if im happy (even before what has just happened), and I cant bring myself to tell her Im not as happy as i used to be. I feel im being selfish if i start telling her that i find sex boring and i dont want to upset her. I've thought about bringing up the subject of sex therapy but I again think this would upset her. Now she is pregnant I feel things could get worse.

Has anyone else gone through similar?
Any advice welcome.