There isn't a spell that will change your gender or age like everyone has said. Just because someone post a spell up here doesn't mean it will work. Sorry but that's the truth, but there are other options, atleast I think so. The rest is just my opinion and what I might do take as you will.
You can get a sex change to make you outer appearance that of a females, but biologically you are still male. That is the permanant part. Now hormone injections can help you feel more like a female biologically but still male. You know who you are and I think that's all that matters. All being a human male does is give you certain hormones and parts and a few other social norms. So you can be a female, maybe not biologically but otherwise. Now if you are looking for a physical change then as I mentioned you can have a sex change but that's rather costly. I would do what you feel you should do to feel more like a female.
Now the two year old part, physical age can't be changed not even science can do it. I do think however you could change mentally to a 2 year old, I don't suggest this at all because it will create problems. Like you lose a job, no money, need of parents. I do think however that you could roleplay as a two year old and by finding some proper help, you could go through some stuff you couldn't as a two year old girl. Just to try to expiernce it as you would like. That's my suggestion and how I see you being able to get the best effect out of your situation.
Also don't let anyone talk you out of how you feel, put you down, or anything of the sort. You know how you feel and they don't, so don't let them get to you. I have seen first hand people getting put down for how they feel and it sickens me.