Why not try some positive visualisation?
Sit quietly on your own with some of your favourite music on which will make you feel comfortable and at ease, maybe a bit romantic.
Just sit and relax for a while til you're warm and comfortable.
Then slowly imagine someone (whoever you want, even an angel) touching you on the shoulder. Stick with it a while, realise it's not a threat to you and try to think how it is actually quite nice and comforting.
Do this gradually in stages in your own time, going to whatever level you feel comfortable with eg holding your hand, sitting right next to you touching, then hugging to various degrees and as far on as you wish.
Then maybe start trying it with your boyfriend, either sit with him and just do it in stages eg sit and hold hands and talk, tell each other how you feel about each other - only nice things - to encourage you to associate physical contact in a positive way.
Maybe have stages where you say go out for a nice walk and spend some quality time together, say hold hands, then link arms, his arm round you, sit and cuddle up to each other.
Explain to him so he doesn't get the wrong idea and take things to far too fast and make it a positive thing. Getting out and about will help this rather than in a home setting.
You can get to this later, hold hands on the sofa, lie with your head on his lap while he strokes your hair, cuddle up together, just sit there and kiss, massage each other and then let it go wherever it does. Make it loving and intimate.
Tell him what you like and want and what you'd like to do to him eg run your fingers through his hair or hold his hand or cuddle and tell him how good things feel. or tell him what's not good and try to suggest something that is so you don't just back away from each other.
Do it in your own time, as slowly or quickly as you feel