I have pains like early labour pains but im not pregnant!?

Im 21 and i get these really painfull pains like ealry stages of labour, they are very painfull, they last for about 20 mins and i have them atleast once day, even if we havent had , iv had them since my first child who is now 2 and i only have a period evry 6 - 7 weeks and it only lasts 2 days, im waiting to see a gynacologist but they keep canceling my apointment, these pains have me in tears and curled up in a ball in pain, it hurts most during aswell. Iv also been trying for a baby for a nearly a year and no luck, iv allready had one and hes 2 now and i never had any trouble gettin caught with him, i got caught within 2 months of trying! These pains are really bad, what is causing them? Please help!