boyfriend

I'm new to this but I'm 17 and my boy is 18 and currently were almost 2 years... but we are running into some problems with me not being open enough and not sharing enough with him. he says I'm selfish also. sometimes little things turn into big issues for us (currently in one) I just want advice from anyone who knows how to get past these types of negative feelings we have and just to be content and not have him thinking I don't want him or anything.