I've got a Squier Tele and I'm so confused by putting new strings on. Worked fine this morning, took off the old and put some new ones on and they are all directly touching the fret-board. Why is this? How has this happened?

Picture for reference of a similar guitar style: [forbidden link]

Whereas in the picture the strings flow over the black diagonal shape at the back, with mine they are tightly pressed against it. As far as I am aware I have not altered anything from this morning.
I can't see the picture, and I'm not too good with guitar maintenance, but what little I know makes me believe the action might be really low.

But, that doesn't make too much sense if the old one's were working fine. Have you tuned them up and everything?
Yeah, I could take a picture. Although it won't be very high quality.

I feel like I'm going insane

Worked fine and I haven't adjusted anything. I am using a 9-42 gauge and I've read having smaller numbers can affect this, but surely not?
You can take it to a shop and ask them if something is wrong with the intonation, although i'm not certain intonation would have anything to do with your action. There are springs you can adjust but I wouldn't recommend it if you are not certain with what you are doing man. Best of luck.
Either way, it is a simple fix for a guitar tech. I'm sure they wouldn't charge more than 15-20. (USD)
Yeah, should be simple to fix.

Be sure to ask the tech if possible what was wrong so you learn from the experience and can avoid it next time.