Sexual identity isn't a matter of gay v. straight. Damagogues and propagandists would like it to be so simple, but let that be their problem.
The way I like to put it is this:
1. Are you being totally honest with yourself about your sexuality and sexual feelings?
2. Are you honest and responsible in your relations with your sexual partner(s)?
3. Do you feel sexually fulfilled?
If the answer to all three questions is yes, then you should be okay, whatever your sexual orientation and activities are.
The rest of your question is more complicated. An abused boy often thinks he's gay because of abuse. That is, he may think that male/male sex makes him gay. This is apparently what your father thinks.
But that just isn't so. Homosexuality is about a lot more than sex, just as heterosexuality is. It's about who you want as your soulmate, who you love, who you want to share your life with, and so on. And in any case, note the word "share". Abuse isn't about sharing anything, it's about a cruel crime that betrays children and uses them for the amusement of predators.
A boy may also think he's gay because when he was being abused he got erections, felt pleasure, and if he was mature enough, ejaculated and achieved orgasms. But our body is sexual in the first place, David, and a boy will often react physically to abuse even when he fears or dislikes what is being done to him.
You should know that many boys are unsure of their sexual identity at your age, regardless of whether or not they have been abused. It's just that the social pressures of our society keep them from talking about it.
For abused boys the confusion is greater, and that's because the abuse has occurred right at the time when you would usually be laying down the foundations for your adult ideas on who you are sexually and what you think is right and wrong. Abuse wrecks these foundations by removing sex from the domain of normal healthy life and turning it into something linked with fear, danger and shame.
In all honesty David, I doubt that you could really know your sexual identity right now. This is something you will begin to sense yourself from activities like dating, close emotional contacts with people, and taking note of who you find physically attractive. You need to give yourself time and accept that however it turns out it will be okay so long as you are happy and responsible in your sexual relations with other people.
Nobody living can ever stop me
As I go walking my freedom highway.
Nobody living can make me turn back:
This land was made for you and me. (Woody Guthrie)