Howdy & welcome here dodiddlyoh.
Firstly, if you are gay, then there is nothing wrong with that. Who knows, you may even be Bi. Again nothing wrong.
You shouldn't be ashamed about your feelings, and please don't think of yourself as a loser.
There is an organisation called QLIFE - an LGBT peer counselling service, google them - it may be a start in understanding some of the confusing things you may be experiencing. Talking things through with someone can only help, it may be hard to open up (at least the first time) but I can promise you that it helps.
I came out almost 3 months ago after a long marriage and kids, after hiding my true feelings for all my life and not experiencing the real me. I have received a great deal of support from family and friends (including my wife), and it all started because I came to this forum and received a great deal of support from peers that had experienced these things before.
Sounds like your sister may also be a great support - if she suspects it anyway, is she someone that you can talk to about it?
Don't be afraid to explore, be safe, but not afraid.
There is a lot of support out there, much more than I'd ever imagined anyway.
It may also be worth looking at talking to a counsellor - a psychologist - I thought "no way - I don't need one" but after actually seeing one was thankful that I did. He drew me way from a real dark path that I was on and offered so much clarity that I am now happy with who I am.
Remember, if you are gay, then that is okay. There is absolutely nothing wrong with that. You can't help being who you are!
This forum is a great place for you to start to seek some help, there are many here that can offer you some very sage advice!
Keep visiting and letting us know how you are.