I don't know what to do...

Hi guys, I hope you are well, the truth is that I have not been doing well mentally, I am not one to express or talk about my feelings, I am a very reserved person with my things, with what happens around me, with everything, I am very pitiful, but with a strong character although I am very tearful. I don't know if anyone will read this, but I will write it anyway because I need to try to unburden myself in some way, today I feel very tired mentally (I think it is accumulated), I am tired of doing things for someone who in the end doesn't see them or value them, and I am not talking about a partner (I don't have one). I'm tired of trying hard, of giving 100% for everything, of breaking my back to give him/her the best, for always leaving me last in order to please that person.
I feel that I have not been a bad person, nor have I behaved badly towards that person, and I really don't think that I deserve bad treatment, scorn, reproaches, among other things. Today I have been thinking that in these last 4 years I have not done anything for me, nor for my future in order to give the best to that person, so that he/she is worthless. I feel trapped, and that I can't get out of there. I feel that it is not easy.