My boyfriend's dad hates me and I don't know why?

My boyfriend and I are both in college, both of us live at home (regretfully...), and we both have jobs, cars, and all that. We have been dating for four months and we are happy together. The thing is, a few weeks ago I saw my boyfriend and the next day after that his back gradually started hurting him until he ended up in the ER. Somehow, his parents assumed I had something to do with this. They called my phone as he was going there. I was asleep early because I was exhausted from my new job. I have never got a chance to explain anything to them about it. Ever since, it seems they have implemented a curfew on my boyfriend. He now has to be home by 11 nearly every night, weekend or not. They say it's because he wakes his dad up coming inside. We only see each other maybe twice a week, but his dad acts like I am a nuisance. I do not dress trashy, talk nasty, I am smart, in college with a 3.7 GPA, have a job, etc. I have my head on straight. I feel like he thinks I will get myself pregnant and drag his son down with me. That is one of my biggest fears and a baby is not in my future. I am dead-set on having a career of my own. That being said, his dad knows all of this about me. His mom approves of me, as I applied to her place of work once and she really liked me, even though the manager above her did not decide to hire me, his parents are divorced. I believe there is a reason they are because his mom is very, very nice. His dad has never been from the start. I know it's his house, his rules, and I understand that, but when is his son allowed to have a life outside of school and work? How should we deal with this? Is is it something about me personally or is this just the way he is? He is a military man so I don't think he is very warm and loving to begin with...