Don't give up too early. Many characters will have better equipment than your Sin has, so you're fighting an uphill battle. As they've also got more experience, the hill is even pretty steep. The first few dozens hours, you'll get pwnd pretty badly - was the same for me when I started pvping with a Sin. But it'll get better.
Maybe join PvE groups/raids to get better equipment.
Maybe keyboard/controller setup is the issue. For example, my settings are not really suited for circle-strafing while doing combos. Combined with the reflexes of a dead duck, I'll never excel in AoC melee pvp, but I know why. Maybe tell us how you control your character, and somebody can give advice on that.