Hi

As Nae Nae said it is probably the ligaments and muscles that support your uterus stretching.

I have found a couple of times recently when I've been walking that I've got what can only be described as a stitch in my left groin area. When I've read up on it it is your ligaments being stretched. Article also said that more likely to occur on left side as uterus tilts to the right. Can happen when walking, when you take exercise when you sneeze when you move unexpectedly ............. basically anytime .............. so nothing to worry about but not really what you'll feel when baby moves - that is more like bubbles