feeling this nauseous feeling since 16. I am now 20

okay so, ive been feeling this nauseous feeling since 16. I am now 20 years old. around the age 17 to 18 i felt okay but the other times i always feel sick and get dizzy. I dont know why. it gets in the way of everything i do. my bf hates it when i say i feel sick or im sick. which even makes it worse for me cause I dont know why i always feel like this and it really bothers me a lot. i have to chew gum to calm myself down. please helpppp meee cure myself.