I say this with all patience as the best piece of advice for you to find the most information on this topic- use the search function. This topic has come up before, and many bright people contributed their insights.
For now, though,
-keep your gun up. Always point it at the opponents, even when you have to bring it behind the bunker with you.
-stay alive. For the love of God, what good are you in the dead box? Even if you don't feel you are influencing the game, if you are in a front bunker, you are pivotal. Even just staying tucked up in it, the other team has to think about you a lot.
-when you break, watch the paint coming at you, not the path you are running or any other distraction. Someone mentioned this before, but it bears elaboration; don't look down, look at those lanes that you are trying not to get shot by. Refer to the previous item.
-don't second guess your primal killing urge. When a little devil on your shoulder tells you to go stick your barrel in some sap's kidney and type a letter to Mom on your trigger, you sign that letter, "I guess paintball ain't your game, sucka, love, Luke." Don't get caught up wondering if you should go bunker the opponent, in other words, go do it now.
-talk to your back guys. You aren't hiding from anyone. They all know just where you are. They can't think about anything else. So just yell at your teammates for information, tell them what to shoot, and if you haven't heard them talk for a second, demand that they tell you that they are alive and not taking a nap. If they are dead, or taking a nap, your responsibilities just got heavier.
-know what is going on on the field. This is a byproduct of that whole running to you bunker with your eyes up. Also, of listening to your back players as they fill you in on all the positions, where the opponents are shooting, and where your teammates are shooting (as well as what they want you to do, sometimes). If your back players or mids die, you should still be trying to win, and doing that requires knowing what's going on on the field, so be prepared for being alone.
-look over your shoulder to see where paint is flying, if you are being pinned down. That ballistic arc leads right back to the next person you need your back guy to tuck in, or you need to find somewhere else to pop out and shoot at that person.
If you had the patience to read this whole post, you might not be ADHD enough to be up front for long, so sart learning to play mid. Then, grab some snacks and learn to play back center.