I can't say certain words that I need to say for my job and it's really bringing me down

I can't say certain words that I need to say for my job and it's really bringing me down I'm 19 and I work at a small pick up Chinese restaurant. When I first started working here, I could say everything perfectly. However, now I can't say "How are you doing" without making the H sound more like a P, and I can't say any price totals that have 50 in it. I've stuttered my whole life and it usually comes and goes but this has been sticking for months now. I feel super embarrassed when trying to say things like "That'll be $7.56" so sometimes I round up to 60 just so I can tell them. I feel terrible for up charging the customers so most of the time I would secretly give them the correct amount of change. However this has stopped as someone asked me why I gave them more change and I couldn't explain why. Is there any way to overcome this? I try saying the words in my head all the time, and I can only say it when I don't imagine people in front of me. It may also help to say that I've dealt with social anxiety in the past which may have had something to do with my stuttering problem. Any help is appreciated. Thanks