My boyfriend told me to F (eff) Off?

Last night my boyfriend was setting up a tv in our room (we live together for 4 yrs now) and he got frustrated with it. I didn't know he was having trouble with it, and I tried to come into the room. I barely had the door open and I asked "How's it going". He yelled "F (eff) Off!" I thought he was joking until I opened the door and saw the pissed off look on his face. I just closed the door. Swearing often happens around here, but he has never really directed it at me before. I was shocked and really hurt. He never told me to f off or f you before. Later he came and tried to apologize but I didn't want to hear it. I just told him to leave for work. Now he's home again and I haven't said one word to him and he hasn't really tried to talk to me (except for a few minor questions like "Is that seat taken?") He has a really bad temper and he has promised on mulitple times that he will work on it. But I haven't seen any attempt at it yet. This has been the cause of alot of fights for us and now he tells me to eff off. What do I do? Am I overreacting? Should I just let it go because he was frustrated?