They used to tell us that pig pregnancy is *around* 114 days, but many things like body condition, number of piglets and even the season can influence that. Generally, if she looks and acts ok, keeps eating and has not temperature/depressed behaviour, she should be fine and get on by herself.
If any of the above happen or if she has foul discharge, call the vet asap as some of the piglets might have died at the front and blocking the other ones at the back, preventing birth of those still alive. Also if they rot, it won't be good for her - but you'd notice she would be so sick.
You could always call the vet just for a scan to check they are still alive.