Parking brake feels like it is not releasing?

When you take your foot off of the gas, it feels like you're pressing the brakes, right? I would say that your most likely causes are (1) a bad brake caliper which is sticking and holding the brakes on one wheel or (2) a brake line which is collapsing and thereby holding brake line pressure on the caliper. First off, you will need to identify which wheel(s) is/are causing the problem. Take the truck for a drive, maybe two miles, then get out and touch each rim. One or more should be much hotter than the others. This is where the problem is. Take a close look at the rubber brake line near the wheel. If it is flat or kinked anywhere, then it is your problem. If not, then it is most likely the caliper.

How to change a caliper and some general information on them: https://www.2carpros.com/articles/brake-caliper-replacement

Go ahead and identify where the problem is for certain and then I will be able to get you more specific replacement/repair instructions.