Does he only do this while manic? Does he take medication?
I think he only does this when manic or heading this way, as when depression hits it's very low, although I wonder if he continues to try give himself a little lift. He takes alsorts of medication, although the psychiatrist states he is hard to control with medication and he has never found a plateau state.
Also, a new twist I suspect he knows I maybe feeling like this as he has now started saying how much he loves me and he feels severely depressed , saying he loves me is not something he normally does
Increased sexuality is a part of mania and can get a person into a lot of trouble. Too those sites can be very addicting and if he leans towards addiction than it may be his newest 'fix'. You need to decide what you will accept and communicate that to him very clearly. If his bipolar isn't under control he needs to go to the pdoc and try something different. There are 3 mood stabilizers and more than 6 antipsychotics plus a few other things, so there are lots of things to try. In addition to lifestyle things like exercise and eating well.
But my (now ex) non bipolar husband got addicted to those sites and eventually left me for his 'true love' so there is a risk of that as well. What I would say is be very clear about what you are willing to accept and I would say that visiting those sites at all should be off limits. That if he feels those urges in the beginning he needs to go to his professionals.
Your answer is amazing, thank you.. This is how I feel but when I try to mention anything like that he goes mad and says I have no idea what I'm on about, why do I feel guilty when it is him on these sites, that's the part I feel difficult coming to grips with! He is on both stabilizers and anti psychotics but the psychiatrist says he is very hard to control, and he has never reached a happy medium. I did face him years ago about meeting an ex and he swore he would never do anything to hurt me, like be on sites and meet exes, but obviously not