Having transmission problems on my 1995 Chevy Tahoe ls 4x4 4dr
 

My 1995 Chevy Tahoe ls 4x4 5.7l and has the 4l60e transmission. Its acts like I have no power when I use the manual gears 1-3 it wont go nowhere same goes for my reverse. When I have it in park it acts like it has a load on it and has no power only revs up to 1600 rpm. I still have overdrive it works but gears slip and still don't have power but it still drives just really slow. My Tahoe ran great yesterday no issues at all, today went to leave the house and had these issues. I did do a flush and filter change on it to see if that was the issues but it didn't help anything still acts the same. Could it be something electrical or maybe a bad sensor? I dont think it's the band's going out considering it ran no issues yesterday. I'm open to suggestions, any tips or tricks would be appreciated.