IM 40 Weeks Pregnant And Have Had Sharp Period Like

IM 40 weeks pregnant and have had sharp period like pains at the bottom of my bump right above the vagina... They will not go away, therefore they have been there all day as well in my lower back. When baby moves it's even worse pain, kind of like really hard pressure. Is this the start of labour? Or could something be wrong since it is not going away? Also, a lot of "Air Bubbles" have been coming out of my vagina since these pains started.. Is that normal?