Welcome here to the forum, I read your other post talking to Risingangel and think the whole question of relationships, maybe with either sex, is a pretty hard one to deal with.
When you think about it forming a serious relationship, not just a few days, is where you take a big risk, giving affection and dependence to another human being, and needing those feelings to be returned. If they are not you feel really terrible.
All the symptoms you talk about could be caused by anxiety, I'm no doctor so am guessing. Can I suggest you go see a GP and in an extended conversation explain waht is happening? There is no need for you to suffer like this long term.
I would think your reactions would be obvious enough for your parents to notice, can you talk about this with them, or another family member? It can help to have understanding people around.
There are a couple of good places to web-chat or talk
Kids Help Line (1800 55 1800)
Both have people - professionals- who are experienced and can be a real comfort.
I guess you, like most of us, need a relationship in your life, and with a bit of a hand from places like these you will get there