Job advice

Tomorrow I go for an interview for a job that came open. It's not what I applied for but the pay is close and the hours are the same. The duties will include unloading a truck and putting up stock in the cosmetics department. Should I tell them I am pregnant tomorrow? (I am fixing to turn 23 weeks) Also, how much will be safe for me to lift? This will be at least 40 hours/week. 
*** I don't have time to call my dr before the interview unfortunately. During my first pregnancy I worked a retail job until I was 42 weeks pregnant that sometimes involved putting clothes out, but I agree this one may be a little harder since it is constant and will be boxes. I felt like if I straight declined this interview they may be less likely to call if the job position I want became available. Thanks for the advice ladies!***