A couple suggestions. Three things I see that may be wrong. One your are not getting enough exercise and nutrients. Two you have too much stress. three your not over your ex.
One if your not getting some regular exercise and good nutrition you can have a lack of sex drive or even just a lack in life. This also can help with the stress but you need to iron out what girl you want to be with. This new girl may be beautiful and nice but maybe she doesn't do it for you. Turn-ons are not always about beauty.
self-gratification is self gratifing it will almost always turn you on. Because you decide the fantasy!
there may be other areas in life that are effecting your mood and causing you stress that may need to be addressed.