I recommend reading and/or listening to Neville Goddard. That has helped me more than anything. Here is a link to his recording of The Secret of Imagining which is less than 17 minutes long and is about how imagination creates reality.
https://m.youtube.com/watch?v=YccI-t1yojk
I suggest that you do what Neville called 'living in the end of the wish fulfilled', which means imagining the ideal end result as if you already have it now. In your case, imagining the ideal relationship with your SP as if it is yours now. Revision could also help you. It has helped me a lot in 'unhearing' some hurtful remarks from my SP that I think weren't intended to be hurtful but I took them that way. In your case, an example of this could be replacing his comment about wanting to date somebody else with hearing him say 'you're the only woman for me, I love only you, I don't want to date anybody else' or anything that is the opposite of what he said that hurt you. Do not attempt to change the situation by trying to manipulate outward conditions directly, such as by trying to talk him into changing his mind or getting somebody else to try to do that for you. It wouldn't work. First change has to occur inwardly, in your mind. Ignore outward appearances as best you can, stay away from looking at any social media he might have or anything that could upset you or cause you to have fears or doubts. It can take time to change things, so give it time, don't despair, be patient, be persistent. As Neville said in his lecture Brazen Impudence, you are the only one who can keep yourself from having your desires by the failure to persist in imagining them.