There's a reason why your parents are unhappy with your decision...
As hard as it may be, are you willing to sit down with your mom and dad and ask them why this upsets them? It may be really hard to hear but it's important to get their honest feedback about the person you are choosing to be with for the rest of your life.
Sometimes we can feel that our parents don't know what's best for us and aren't willing to accept our choices, but they may see something in him that you don't.
I think a parent wants their child to be happy, but in talking with some friends of ours who have five daughters, I asked them if they would have personally chosen any one of their son-in-laws for their daughters and they answered a resounding no!
Before going into marriage, it's super important to prepare for marriage instead of a wedding day. What does this mean? It means going for pre-maritial mentoring or counseling for 4-6 sessions. Or, participating in a marriage seminar that will help you talk about communication, conflict, family of origin, sexuality, money, leisure activities, and parenting are a few examples.
Does this man have a stong relationship with Christ? I'm talking about one where he has accountability with other Christian men, one where he spends time in God's word each day and is a regular church attender. When you are together, does he pray at each meal and suggest praying together or over the phone? These are just the first steps toward looking for a man with the desire and goals for the spiritual development of his marriage and his family.
Is he willing to work on furthering your communication and conflict resolution skills? You've had your share of conflict from what you've said, this may be an area to dig deeper into and get some tools for your marriage toolbox.
Mom and dad may have their reasons. They may be valid and they may be completely unwarranted, but it's important to hear what they have to say. Then make your decision whether to still marry, or wait based upon what they say. Sometimes people in our lives see things in others that we do not.
Growthtrac has a great compatability test that is wonderful!
http://www.growthtrac.com/checkup/
There is a great book by Les and Leslie Parrott called
Before You Say I Do that I highly recommend.