Depends if you are better at catching, throwing, running or blocking (as opposed to tackling). Fullbacks and Tight Ends do a little bit of everything - blocking the QB or running back, sometimes catching the ball, and the FB sometimes catches it. The running back focuses more just on running and catching and blocks less.
Cornerback wouldn't be too bad. You get to run and hit the QB or half back, you usually don't need to be extremely strong to do that. Maybe you could go with safety, they knock the ball down, go for interceptions or stop people running or catching the ball. Linebackers usually focus on stopping the run or blitzing the QB and sometimes covering receivers. Tight End and Full Back require a little bit more strength.
But yeah I'd say HB. You don't have to catch the ball too much, you just get it handed to you and run as fast as you can and try not to get hit.