I don't think "normal" exist. If you feel something is wrong then it probably is. Seek for help for you and also to have free time from your toddler.
It’s normal for a stressed mom with a toddler to cry sometimes. Taking care of a toddler can be really tough, and it’s okay to feel overwhelmed. If it happens a lot, it might help to talk to someone or take a break to recharge. Self-care is important.
I’m not sure what’s a “normal” amount but if you’re crying daily I think it’s worth speaking to a doctor. I know when I was really depressed I was crying all the time, over small things too so that can definitely be a sign