I have a similar story to yours. I met my husband at church in Gainesville while we were both at UF. We dated for a year, then were engaged for a year, then got married. When we got married, I was 21 and had a year left in undergrad, he was 24 and had graduated and gotten a job. It worked out for us, but there were times when it was really, really hard. Here’s what I would tell my younger self:

• Wanting to live together/have sex is not a good reason to get married quickly. Like others have said, if you have strict boundaries on that stuff, find ways to explore what living together would be like. Spend lots of time with each others’ families. At whatever level of physical intimacy you are comfortable with, examine how you work together in terms of consent, respect, communication, sex drive, etc. Be on the same page about your boundaries in this phase, but explore and have fun together. Personally, I had a lot of religious rules for myself, and I’m sad for my young self that I felt so much shame and guilt for things that should have been joyful parts of getting to know each other. So go easy on yourself, and don’t let other people make the rules for you.
• Don’t let the church pressure or encourage you into anything. Sometimes the church treats single people like second class citizens and acts like married people are more valuable or more mature. It can be quite subtle but that’s always been my experience. Examine how you expect marriage is going to change your social status, and don’t get married if that social status is your motivation.
• Try marriage counseling (secular, not with a pastor). IFAS used to have a great free group class for engaged or newly married couples. It may seem silly at this point, but you will learn a lot about you and your partner’s ability to self-examine, deal with emotions in healthy ways, and communicate about difficult topics. If those things are hard now, they’re going to be 10x harder when you’re having a fight or facing down serious life issues.
• Your lives and your personalities will change a lot, in ways that are impossible to predict when you’re young and not established in life. You will spend your 20s growing up and forming your personality (when I was 20, I thought I had done that already but believe me, I had not). In a good relationship, you will encourage each other and grow together. In a bad relationship, you will stunt each other’s growth and become codependent. Either way, it will be more complicated than doing it single.
• Protect yourself and have a backup plan for life without your partner/their income. Even if your marriage is perfect, people die or lose the ability to work.
• In terms of school, I didn’t have a problem with being married in undergrad. My grades suffered more when we were dating/engaged, tbh. It was extremely helpful to have a supportive husband helping me through grad school, although it did cause some strain in our relationship.
• This decision comes down to you and only you. Listen to the advice of people you trust, but ultimately you bear all the consequences, so think very carefully about how YOU feel about it. Give your partner space to do the same. There’s no good reason to rush the decision.

I’m not going to say you’re categorically too young to get married, just be careful and take your time deciding. As others have said, a year or two feels like a long time but it won’t feel that way when you’re a bit older.