Im not the relationship expert and maybe taking advice from me is like accepting a condom from Edward Scissorhands ..not a good idea..but I agree with Silk.
I went through the same situation and it all boiled down to personal insecurities. I took her to get her nails done and all that, because when a woman feels beautiful she is confident. After it all she said I look sexy and she doesn't feel sexy so she just gave up and knew woman were checking me out and it upset her..even though I came home to her everynight and only ever wanted to be with her.
Sit with your woman and try to come up with a solution together, even ask if she is interested in doing the same as you and don't forget to make her feel special, she has to know that she is special to you and aa priority not an option. It has to be discussed and communication is the key to any lasting relationship. Do remember this..not every woman finds big and bulky attractive..I was lean 6%bf at 200 at 6ft and women said I was sexy as hell, when I went to 225 I didn't get as many compliments..thats just how it goes.
Good luck buddy