The link between previous experiences and lack of physical contact is there...
You say that alcohol helps you be more physical, suggesting that when you drink you become more relaxed, and that the problem is that your not comfortable with doing these things yet. Silverwings, for example, had a similar problem but by making a bit more effort has become much more comfortable around people. I think it is just something you have to go for, the more you do it, the more you will feel comforatble and in time you'll be able to initiate physical contact with ease.
Just to make the link;
You said you were bullied... you didn't mention anything positive (RE: physical contact) therefore we can assume that most of the physical contact you have had has been negative. If this is the case, then when presented with a situation calling for a positive response you tend to lack the resources to deal with it because that is not what you 'have learned'.
I suppose one idea as well would be to slowly build yourself up, but this involves me giving you advice to drink more alcohol lol. Simply drink, then note what physical contact you give and how much you had. Then next time drink less/none and try to do everything on the list. I know it sounds kinda weird walking round making a list, but it can only help!