My dad does not understand me?

Well, im 14. My dad and I used to be close, but in the past 7 years or so. He will get very angrey a lot. I love my dad but he will get angrey and will go off just whenever. My mom thinks its high blood pressure. I think it might be also. He's nice and funny and sweet and dad-like at times but then he will be angrey the next. I can't even have a normal conversation with him without worrying i might say somthing that would anger him. He hardley ever goes to my Swim Meets and seems to mostly work out side or in the basement and stuff. Hes 62 btw and fought in Vietnam, so I alwase thought that maybe thats why hes so strict at times. I don't get it though. He will lecture me about stuff most little kids know, and even if I respectfully say "I know" he will act like I don't know. A few months ago he tried to tell me "Don't you dare text while the meeting is on." and I was like "Yes, sir, i know" and he was like "It's alwase very rude to text during servises" (Refering to some boyscout thing that was going on that my brother was in) and i would just be like "Yes, Sir" but he wouldn't stop telling me that, and it was like common sense that I wouldn't do that. I would never do that during my brothers event! It was like he just wanted to hear himself lecture me about things. Then he will yell at me occasionally and it would make me upset. Its his way or no way. I love my dad, but sometimes. . . I wish I had a normal dad. . . what should i do?