What should I do??

b

So today I started a job at the post office, it requires A LOT OF LIFTING. I started to cramp this morning and also on my way home. I worked 4am-9:30. I have to got back today from 5pm-8pm. I’m not sure if I should continue this job. Should I? I’m very nervous. I have to lift a lot of heavy things. I just don’t want to look bad. I’m in the holiday help at a post office