You won't lose your identity. From the sound of it, you aren't some silly 17 yo girl who's getting married because it's finally legal to do so without your parents' consent and you're in LOVE with some 19 yo guy- you are going into this with a more developed identity.
In relationships, there are generally 5 phases- 1) The Shiny New Toy Phase, 2) The Conflict Phase 3)the Comfort Phase 4)The Commitment Phase 5)The Bigger than just the 2 of you phase.
The Conflict phase is all about saving your identity. It's the bit where you will get into a dumb argument about how he made scrambled eggs for breakfast because he ASSUMED you liked it that way because HE likes it that way, but you like them sunny-side-up. Just like something small like how you like your eggs is suddenly a vital part of your identity, the bigger things will seem very important. Conflict is about "THIS is who I am. I will NOT do what YOU want all the time for THE REST OF MY LIFE!!!" Everyone I know who has been in a relationship for over 6 months experiences this, no one's body is built to be in that drugged up chemical high you get in the beginning, you'd wear out and die if it weren't so.
Now, the other stuff. Think about it like this- it's 2 separate commandments, 1) don't do anything before marriage 2) Now that you're married, you have to. It's not a conflict. It's just demonized to keep people in line for that first commandment. In the more recent past (in 1800s-1900s Europe) we have proof that it was seen as more of a part of life, plain and simple, by a significant portion of Jews (if you want to research this, go ahead, but it's not for this website). So yeah, it's not just Biblical Jews who had a more chilled attitude- it was our great grandparents. The new attitude we were brought up with is precisely that- NEW. Wanting to feel more relaxed about the whole thing is in line with the vast majority of our tradition. You aren't sinful at all. You're normal.
To shift gears, the first thing to remember is that it's 2 separate commandments. Secondly, think about all the people who were shomer/ just shaking hands and go on to happy marriages. Thirdly, you are wired to get over it- it's the one thing you KNOW your ancestors did, you know what I mean? People who don't really get over it tend not to have many kids.
Fourthly, this guy is not a stranger. You have been dating him, you know him somewhat. In the experience of most girls/women/whatever people my age are called I know, it is a LOT harder to open up in the feelings/thoughts department than the physical. Sharing that sort of stuff is scarier than your body. Why do you think the FWB thing took off, it's all about compartmentalizing your life and stopping the other person from getting too close, and guess what? It doesn't work. If you don't want to open up and be vulnerable, you're going to end up being vulnerable anyways.
Marriage is about 2 people- 2 people with baggage, self-esteem issues, skeletons in their closet, pasts, insecurites- who decided that they were compatible enough to make it work. No marriage is on Easy Street. My married friends tell me about their married friends and themselves- no one is issue-free. Marriage forces you to confront yourself. The idea seems to be that you and the guy become aware of issues you didn't know you had and you work through them in between caring for the baby, working, school, and gaining weight. Let's put it this way- if your only issue is this Kallah class thing, consider yourself and your guy very blessed.
Finally, the chances that you won't be able to deal with it within a year are small, but if you fall into that category, there are people who can help you.
I wish you 2 a happy life together