So confused

Bottom line is I'm married gave been for 8 yrs been with hubby for 10yrs. 5 months ago I met a younger nan for coffee now in an intense sexual emotional relationship. Recently I found out his liking lots if females posts on fb I went mad and gave been co aimed with looming at his page and feeling overwhelmed with insecurity.. He told me I'm his gf- I believed him I'm in love with him he's in love with me but these feelings of raw jealously won't go. I don't know how to handle this I feel psycho this is my first affair. What started off as fun us now do intense and on my part I feel so suspicious- please advise me what to do feel like I'm going mad.