Yep, inserting extra lube with an applicator was really helpful for me too. It was right around 4 months post-op that I started noticing a lot of difficulty with tightness (which I'd never had before). My doctor said that it was scar tissue contracting, and recommended very gentle massage for 2-3 minutes, right before dilation - put a finger about an inch inside and press very gently around the whole entrance, using a bit of lube if it helps, and see if that relaxes the muscles and breaks up the scar tissue.
The more it hurts, the more you will tense up, which tightens those internal muscles. So part of the problem is going to be finding a way to relax, which I realize is easier said than done; whatever works best for you to relax overall (pleasant music/glass of wine/hot bath/etc.) will probably help.