Hi Maria and welcome to the forums
Sexuality can be a confusing thing. Some people just know, however I was not one of them. I was confused. I knew I liked boys, but part of me was attracted to women as well. It was confusing for me. I started dating a boy, and I thought, there is my answer. I am straight. Years went by and we broke up. I then had these thoughts again. I was confused, and my anxiety flared up (my generalised anxiety, not just about sexuality). I decided to talk to someone about it. I was going to headspace at the time. This is a free mental health care service with various locations in Australia (for more info see www.headspace.org.au). He was really good about it and told me not to be afraid of it but to explore it when comfortable. I decided to go on a few dates with women. I now identify as bisexual or likes people not just gender. Sounds like you maybe in a similar boat to what I was in at 16, so thought I'd share. It took me till I was 23 to discover I was just me and I liked both genders. I also know people that had confusion and discovered they only liked one gender. It is ok to not be sure.
There is a thing called a Kinsey scale. This means sexuality is a spectrum. So no one is 100% straight, 100% gay or 50-50. Everyone lies somewhere in the scale. Although you can not choose where you sit in the scale you can choose how to label yourself. E.g. if you are 75% straight, you may label yourself 'straight/heterosexual'. Or if you are 35 gay you may choose to be labelled as 'bisexual'. You can also choose not to have a label. I can just say, hey I like people and their heart I'm just me.
I also am not in the middle. And that is ok. I had to talk about it because I was so unhappy with these thoughts and it made me not comfortable in myself. I had to be ok with myself having attraction to both genders to be happy in myself. I think I'll end up being with a man. I find it comes more naturally for me, however without this journey of self discover and learning to love myself regardless of sexuality, I couldn't be truly happy. I think this is something that maybe you need to discover also. You don't have to take this journey now. I didn't right away. Took me a few years. You can do it in your own time.
I hope my journey as allowed you not to feel alone. I don't think the confusion part of sexuality is explored enough on tv/movies
Try be happy in your relationship now. It doesn't matter if you are happy now with him