I am a 20 year old man and get red eyes every day?

I am a 20 year old man and since my 15 years old more or less I get red eyes every day. I don’t know why, there are various reasons that cause me red eyes, so I don’t know what it the problem.
Sometimes I get red eyes just for nothing, sometimes when the sun is strong and I don’t use sunglasses, sometimes when I don’t sleep enough, everytime I go out at night and feel my eyes are tired and they get red. And my eyes aren’t just a little bit red, they get so red to the point that all the people around me notice it and causes discomfort even to them. I have already talked to a doctor but I think she doesn’t care much and says it must be allergies, but I think it’s not because I have red eyes everyday and I don’t feel like I have any other allergy symptom. She prescribed me an eye drop named Allergodil, and it sometimes reduces the redness a little bit but most times it does nothing.
I really need help because I don’t know what to do anymore and because it is a thing that really affects my life, especially my self-esteem.
I hope you can help me.

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