I want a baby 😔

I'm 21 years old and so is my boyfriend of 2 and a half years. We're currently on our last year at university and are both planning to attend grad school (he's going to med, I'm going to occupational therapy). We love each other very much and both want to get married and have kids in the future. Recently, I got on Mirena. From the moment I got it I felt very sad because I knew I wouldn't be able to get pregnant on it but it's also the reason why I got it in the first place. I want to be financially stable and married before I have a child but I can't shake this feeling of wanting a baby now. I understand I'm still very young and I need to continue to study to be able to provide for my family but it's like my biological clock is telling me I need to start having kids. Every time I see a baby I think it's so adorable and I just want one of my own. Having Mirena means I won't get pregnant and it just makes me really sad 😞 how can I shake this feeling I get of being incomplete because I don't have a baby? Is this even normal?