Kristina let me break it down for you - from what I can analyze from your relationship is that you NEED him thats why you don't want to let go off him.. you may also love him but at times like these you feel there is noway out because you need his help with some financial issues i.e bills.
His telling you not to add him on facebook? I do that to the girls I want to hide things from... the reason he gave you for not being friends on facebook is what i call Bullox, its just a massive excuse and for agreeing to it that just shows you can easily be manipulated.
Your paranoid but being paranoid is much better than being willfully ignorant; I personally think his cheating on you maybe not with the girl you think but if you two live in different locations and don't have a solid relationship then your just wasting your time holding on to false hope.
Focus on yourself, find alternative way to pay your bills rather then rely on this guy because one day I reckon he will just ignore you and leave you to struggle on this matter & for heaven sake break up with him. If I love a girl and she wants to speak to me I would make sure that I am there for her even if i have to fly to California to do it. Your so hurt that your telling us your personal problems and it isn't very smart.
Anyways good luck with whatever you do Kristina, from that small avatar next to your name i am assuming is you.. you look very pretty!