could i be pregnant

Hi iv had the marine coil in now for over a year and never went back for my 6week check up as my medical card got stopped iv 2 beautiful kids 1 and 2 year old.. My periods are 4days late and this never happens there always about a day or 2 late.. iv been getting period pains now the last 4 days and the day they were due i think i had a little stain of pink when i wipped myself but thats it no more bleeding has appeared yet iv also been waking up last few nights with hearthburn, waking up to urinate during night and iv been so tiered lately but the funny thing is my tesco pregnancy test said negative anyone help me please it would be great xxx