Thank you for asking this question. I can hear your sincerity in wanting to please God and I am so proud of you. When I read your question, I thought of Psalm 51, when David cried out to God from his heart after he had committed a sexual sin with Bathsheba:
“The sacrifices of God are a broken spirit; a broken and contrite heart,
O God, you will not despise.” (Psalm 51:17 ESV)
I believe God has forgiven you, as He is pleased with a repentant heart. He will not despise or forsake you! It must have been a very tough decision to break up with this guy that you cared for. However, I want to affirm you that you definitely made the right choice!
As our good, good Father, God’s desire for you is to be with a man who will not only love you, but also commit his life to you. He created sexual intimacy to be a precious gift between two people who love each other and are committed to one another for life in a God-centred marriage. If you felt that you needed to give him sex to earn his love, then it was a transactional relationship, and not a relationship which God desires for you.
To answer your question, no, you do not need to marry your ex for this reason, even though sex is meant to be enjoyed between husband and wife. It is entirely possible for you to find a new partner in the future who loves you with no strings attached. My hope is that you will choose someone who wants to honour God as much as you do, and who will respect your boundaries and desire to save sex for marriage. There are many wonderful Christian ladies who have had pre-marital sex but repented wholeheartedly. If their partners chose not to pursue purity together with them, they were able to move on and found new godly partners. We encourage you to read My (Last) First Kiss Was at the Altar on page 34 for a story about a couple who have both left behind their pasts to pursue purity together.
It is not an easy journey, but it is possible with the support of your community. It is important to pray that God will restore you and cut off any unhealthy ties between you and your ex that may prevent you from fully moving on. Ask trusted Christian leaders or mentors to pray with you to prepare your heart to be ready in the future for a new relationship, if that comes your way.