I would just keep an eye on it. Some stretching pains can be pretty severe, especially since it's your second baby. There's scar tissue and stuff from your first baby. (At least that's what my Dr told me lol).
Have you seen a doctor yet? Some people do not have morning sickness. Some get it early some in the middle some at the end.. Some have it the whole time. The biggest thing i had was being so tired and sleep alot. I did not have a lot of morning sickness. But i would talk to your doctor if you are worried. Plus some woman hurt from stretching.