Lifting

Hey guys so question: I work with adults with disabilities, and I have 2 clients in wheel chairs who need to be lifted up, bathed, etc. One of them is really heavy and usually needs 2 people to put in the lift and too change. I already had back problems prior to pregnancy (a relocated disc) and it was already tough physically to work with them but I refused to work with these two due to my personal uncomfortablness now. I'm 9 weeks. What is the max a person should life during pregnancy? & am I crazy for refusing these two clients? I do this casually, so there are other staff to work with them. One girl just looked at me like I was crazy when I told them.