Maternity leave.

I'm 32 weeks and I am still working just fine. But sometimes I get crams and get sore and really exhausted from work. But its nothing to serious. I am 16 so there are a lot of chances of hacking problems such as an early labor. I am always on my feet and we get pretty busy a lot so I am running back and forth stressing a lot. For the most part I work just fine though. When should I take maternity leave? I will probably ask my doctor just want opinions.