Dating my brothers best friend

I started dating my brothers best friend (Jay) in November of 2014, but we didn't tell our families till last August. 
Recently, I have been asserting myself as an adult more, & demanding more freedoms from my controlling mother, and it's been going awfully. 
 She now thinks that I don't care about her unless I need her for money or to ask her something. Also, her and my brother have come to the conclusion that I have changed since last August & think it's because I am dating Jay. 
I will say this: I feel that Jay and my brother have not been close since we started doing & I don't know why. 
I'm just really lost and confused right now & I want some insight on if this dating thing was bad or not & what to do. 
I love Jay, he's my world and I cannot invision myself with anyone else. We've been through hell and back together and he's my rock. I don't want to lose him.