Salam sister,
Firstly, it is completely natural to feel this way and the fact that you're desires are not fulfilled is not your fault, not Islam's fault but actually the fault of your parents and society.
The Messenger of Allah encouraged young people to marry early so that they may find love with their spouse and so they didn't fall into zina or be in your position
Narrated `Abdullah: We were with the Prophet (ﷺ) while we were young and had no wealth whatever. So Allah's Messenger (ﷺ) said, "O young people! Whoever among you can marry, should marry, because it helps him lower his gaze and guard his modesty (i.e. his private parts from committing illegal sexual intercourse etc.), and whoever is not able to marry, should fast, as fasting diminishes his sexual power." (Bukhari)
Islam encourages sex within marriage but not outside of marriage. For example, when Jabir Ibn abdullah got married for the first time (at 17), he married an older woman. The messenger of Allah joked with him and asked why he didn't marry a virgin so that "she could play with you and you could play with her and she could make you laugh and you could make her laugh"
So the point is, don't feel ashamed of your thoughts and desires, it's Halaal and should be fulfilled if in marriage but of course outside of marriage is haraam and from my personal experience with what I've seen of people, I completely why relationships are haraam.
How many relationships have you seen that end in catastrophe and misery? Wallahi I'm currently in sixth form and every relationship I've witnessed has resulted in a break up causing complete heartache and misery. I'm not saying this cannot occur in marriage but it is far less likely and less common and I'll explain why.
In this hypersexual society, people engage in relationships for sex primarily. They may look at the character of the other person but they don't plan to remain with that person for long. There is no loyalty in a relationship, it's simply playing a round for a few months and then a break up. The reason there's no loyalty is because there really are no consequences in break up and with all respect to my non Muslim brothers and sisters, many relationships are and make people animals because animals engage with others for nothing but sex
However in marriage, the consequence is divorce. This means that when a person looks for a husband or wife, they spend a lot more time learning about the character of person and they will not marry unless they find the person a complete match for themselves unlike in relationships where many form from meeting once in a party and getting drunk.
Before any non Muslim tells me that relationships are good and do encourage loyalty let me ask you a question. "Do you see yourself marrying and spending the rest of your life with the person you're in a relationship with?" If not then that's not loyalty and you're probably engaged in the relationship for sex like an animal (once again with all due respect)
I know this long sister but please. Firstly, don't feel guilty and secondly, become closer to the deen. Listen to beautiful Islamic lectures and beautiful Quran recitations. My personal favourites are mishary, fahad aziz niazi and imam muda mujahid Ibn suhaimi