Dear Tom, 

From the information you give here it seems there is much reason to think God may be calling you. It is good that you are in touch with your chaplain and talking to him about this. As he gets to know you better, has you work on projects, sees how you do with the youth group at your parish, he will be able to give his advice regarding your vocation. God doesn't usually give more signs of our call than the 'inner voice' (our thought that, 'maybe...') and an 'outside voice' (someone else, like your chaplain, who can tell that it is not our imagination). 

Your main problem seems to be your parents' reaction. Their suspicion that you are having the vocation pushed on you is frustrating. Of course. One good result is that you have really examined yourself and seen that it is not someone else forcing you, just you wanting to do what God wants of you.  

What you should do under these circumstances, and how you should obey the fourth commandment (which tells us to 'honor' our father and mother: when you are a minor 'honoring' usually means obeying; as you get older it means holding them in respect, but not shirking what your conscience shows you is your duty) depends on your age, and on the advice of your chaplain.  

If you are still a minor you can insist with your parents, but if their answer is no for now, then you just have to stay put geographically. By that I mean you won't be able to go away to a seminary. But you can still move spiritually: grow in prayer, in your work with the youth group, in your knowledge about the vocation. Examine if God is calling you to Diocesan priesthood (like your pastor) or to a religious Congregation. Visit seminaries, prepare the way.  

If you are old enough to make a step this Summer, then get ready for it - unless your chaplain sees something you need to work on before joining the seminary.