too tight

Okay so I'm apparently extremely tight. Like to the point it's effecting my 4 year relationship because I can't have sex.  I have been to the doctor twice and they tell me nothing is wrong... but whenever we try to have sex or I try with a dildo it feels like there's tearing. I have FINALLY gotten comfortable with fingers. I can get up to three but when I try with a dildo I can barley get the tip in without the tearing feeling. I'm thinking of getting dialators. Has anyone used them and could tell me about how long each size took to get comfortable?  Or if anyone has any other suggestions to help me? Not sure what else to do and it's having a negative impact on my relationship.