Recently I broke up with my girlfriend, but now I am experiencing guilt because I engaged in sexual activity with my ex. We did a lot, except penetrative sex, such as hand jobs, oral, and sexting. Now I feel like I should remain single my whole life because I believe whoever God might have had in store for me deserves better. I do not want to hurt them, and I feel like I have no purity to offer them now. Is this what I should do?
You need to restart your life, living it God's way. Yes, you did a lot of things you had no business being involved in, but it doesn't mean you can't change and become pure. "Do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived. Neither fornicators, nor idolaters, nor adulterers, nor homosexuals, nor sodomites, nor thieves, nor covetous, nor drunkards, nor revilers, nor extortioners will inherit the kingdom of God. And such were some of you. But you were washed, but you were sanctified, but you were justified in the name of the Lord Jesus and by the Spirit of our God" (I Corinthians 6:9-11). If you mark yourself as tainted, you will leave yourself vulnerable to sexual temptation, telling yourself things like "Well, I'm already guilty, so it won't make any difference."
Not only do you need to get yourself right with God, but you also need to learn how to properly treat a woman. Your past relationship didn't last because it was based on selfish physical actions. You did not develop a true companionship or respect for each other. Even now you see any future relationship in terms of physical acts and you are disappointed that it won't be novel. However, you can offer some woman in the future a kind, caring, respectful, and faithful husband -- if you are willing to learn and change yourself completely.