@Malia12 , do what you want. The most simple thing you could do is to write down the pros and cons. I am 20 as well, still so young but yet there's people much younger who have children and they cope. It may not be the most ideal situation but if you do really want this then go for it!
I had a miscarriage back in January and it was by far the worst experience of my life. My reaction was very similar to yours, sheer panic and run to the abortion. However, after a good think me and my partner decided to go ahead and keep the baby as no way I could by choice go through that again...
It's very stressful at the moment as I have just been offered a place at uni start in September 2018 and the baby is due Nov/Dec (that will be going on hold now) and my partner has just started his training for the Royal Marines so of course, everything is up in the air at the moment. I am worried about every little thing but I have every hope it will work out...
That's my story, I know it's a bit of a long one but it's best to hear other people's stories so you can see that it's not all doom and gloom and that there are other people in very similar situations!
As for telling your family/friends, yes it might be a shock for them but I'm sure it will be fine once it's sunk in, like it did for you! Also, the holiday thing, I wouldn't worry about that! I've just booked a holiday today so it will be absolutely fine for you going away!
Hope that helps xxx