back pain!!!

So tonight I went grocery shopping... the buggy was full when I was done($200 worth of stuff) & when I got home I unloaded it out of my car alone, because my mom is always at her boyfriends house so I practically live alone, & now my lower back is killing me!!!!! I can't get comfortable to save my life!! I don't know what to do to make it go away since I can't really take anything, was thinking about getting in the shower and letting the warm water run on it but it even hurts to just stand there.😩😩😩😩😩😩😩😩