If i think my eyesight is suddenly not as good does that probably mean i need glasses?

I'd be surprised if you noticed a sudden change. It's usually more gradual where you notice yourself not being able to do things that you could in the past. If it's sudden, could be eye drops, something in your eye, an infection. Worth seeing an optician, though.

When I turned about 45, I went and took an eye exam and found out that I needed reading glasses but that was all.
If you're worried about it and this problem persists? Just go get an eye exam and you'll feel better inside.

If you're like me then you notice and know that your eyesight is changing or has changed. I know mine isn't what it used to be and I have to use reading glasses from time to time which helps...but I haven't had a real eye exam to see just how much it has changed yet or what may be the cause. I do fine the way it is, but I know I will need to do that eventually and I will when I have insurance/can afford it again.

Being tired, too much reading or screen time, medication, etc.

I'm 49 and my eyesight hasn't changed

An eye exam should provide an answer.