Hello, it's good that you've come forward. Not many people would have the courage to do so.
I can relate to you in that i've experienced wrong sexual thoughts. Now I don't know if you are christian but since you said you're dealing with demons so you're either speaking metaphorically or you at least believe in evil spirits. Whatever the answer, I would suggest visiting a local church :)
If you're Religious or not the people there are a loving family, you don't have to share all the details but tell them you are struggling with sexual temptation, and that you need support from caring, understanding people, churches are full of them! Everyone lusts from time to time, it's something everyone can relate to.
Try talking more in depth with the local priest, vicar or pastor; they won't judge you they deal with these things a lot so just whack it a try. Explain to them how you feel, ask them to get rid of the thoughts or demons inside you and they'll probably pray for you and offer some advice.
Be open and have faith!
Outside of a supporting community try seeking counseling from a professional; the councilor shows you what to do, the community is the muscle that drives it!
I hope I've helped.