Remember exactly what you say in an act of contrition: “I firmly resolve, with the help of Your grace, to sin no more and to avoid the near occasions of sin.”
To start with, as others have pointed out, it is not a promise, it is the willful intent to not sin, at that moment when you say your act of contrition. If, when you say that, you do have that intention, you aren’t lying.
The most important part here, too, is that the sacrament is conferring on you God’s grace to help you in your struggles. There’s nothing at all more powerful than God’s grace. In receiving it, you are given the special fortitude to resist temptation in the future. That does not mean that you cannot or will not sin again in the future, but getting that “shot of grace,” as my confessor puts it, goes a long way.
Tell your confessor your concerns and fears about relapsing. He will offer you advice and strategies on how to overcome sinful behavoir in your life. You may ask him, too, about spiritual direction, whether he can offer it to you or if he can point you towards some resources for finding a spiritual director. Be careful, though, as you ponder and pray about your situation, that you don’t fall into the trap of thinking that your sinfulness is beyond God’s abilities. While it is not “okay” to commit sins, it will be okay in the long run if you ask for God’s forgiveness, though don’t write off the gravity of sin by telling yourself “It’s all good, I can just go confess it.”
Long story short: go to confession.