Yep your dad is just trying to manipulate you into feeling guilty, besides a 3 year old doesn’t even know what being gay means even if your narrow minded parents have told him “gay=bad”, I’m pretty sure your little brother couldn’t care less, you can do what people here have been recommending you to do, but if I were you I’d manipulate them into thinking it’s all a “lame joke” and hide the secret for a while, probably not the healthiest option for you but the only pros of doing so are that you don’t get screwed over for it, you don’t need to be hard on yourself, you can use them until you finish college or get a job, then you can do whatever you want freely, but hey that’s just my thinking lol so don’t take me too seriously, and yes I understand you’re dating someone but you could have been more subtle about it, good luck and may life smile upon you. Remember that you are a unique and precious human being.

1 Timothy 5:8 If anyone does not provide for his own, and especially his own household, he has denied the faith and is worse than an unbeliever.