Does anyone know anything about dogs? (Help)!?

I have a puppy for like 4 months now i was so excited when I finally got him. But since the beginning i was very unhappy with him. he started out by being aggressive and i have a very small sibling so my parents told me to get him trained so I did. He got better for a couple of weeks but now he's doing it all over again biting, barking, growling and I just cant take it anymore I didn't get a puppy to go through hell I got a puppy so I could love him and care for him. But this is what has had me going crazy for a couple of day now I found a tick on his eye and it got me BAD when I say BAD i mean bad I couldnt even touch my pup I was so disgusted I thought I was gonna get infected or something its like my feeling toward him changed I feel horrible every I cry just thinking that he had that on his eye I taking to the vet this weekend but I just don't want to deal with it anymore every time I would think of the tick in his eye I would start scratching and getting goosebumps I need help I don't know what to do I feel horrible I wish I had never gotten a puppy it does sound kind of messed up but I just got it bad I so sad because I loved him soooooo much and I was really looking forward to having this pup around for a long time so could anyone give me their opinion on what to do and what they think ps: serious answers only thanks. !!