1996 Chevy Blazer Galloping

I'm not sure if it is the cold weather because last winter I did not have this problem.

But recently my blazer has been giving me issues when it comes to changing gears while driving. It usually changes when the line hits 3 on the dashboard but when I hit the gas it gives me a hard time accelerating. The line dances around the 3, the car starts to gallop and it wont move past 35mph. Can someone please tell me what the problem could be?