blowjob problems

around last Christmas I was giving my boyfriend a blow job, when things started to go wrong. I was deep throating when I started to gag which is never a issue and he enjoys, however this time I puke a little bit. it made me so uncomfterable that I ended up going into the bathroom and crying. he came into the bathroom and promised me that everything was okay and he understands. however since than I am afraid or nervous to give him a blow job because I feel like it's going to happen again. I try to get myself to do it but then I get  overwhelmed don't. how do I take my head of out of and start to give him blowjobs again, because I enjoy it myself and so does he.