Gallagher has also had loan spells with Stoke City and Preston North End, but he fears he has no future at Ewood Park.
"I've not really spoken directly to Sam about my future," said Gallagher.
"I went back to Blackburn for some treatment when I had a bad knee and shook his hand. The next thing I knew I was watching Sky and it said they were willing to listen to offers for me.
"To me that is pretty clear. It has been a long time coming that the club will say they are prepared to let me go and I will look for something new in the summer.
"When Sam came in I thought it might be a chance to get back. Blackburn were not doing well, and are still struggling, but it never happened.
"That was a kick in the teeth, but now I've got my head round it."