Yes or no?

Yes

Yes loneliness hurts,

But you can still be in a relationship and be lonely too!!

I am in a relationship but still feel lonely as hell

It's supposed to hurt.
People are lazy (efficient) group creatures.
They don't do anything without being prodded.
Fear, pain, nervousness, loneliness, all increasingly stressful prods to do something.

When you're hurt, you seek to solve it.
How do you "fix" loneliness hurt?
You find other people.

There are more than 7 billion potential cures for loneliness on the planet right now.

So, of course loneliness hurts.
It's supposed to.
No man is an island, no man was meant to be an island.
When you try, you will work against yourself succeeding at it.
Being hurt by loneliness is ultimately a choice you have complete control over.


Then either:
- you made the wrong choice in who you are in a relationship with.
- you don't know how to value what you have.
- you expect too much from the other person.
- communication sucks in the relationship, you don't really feel lonely, but you feel there is change or some sort of problem, but "lonely" motivates you in the way you want to address the underlying problem. e.g. you want out of the relationship, but need a reason. you want to have sex with someone else, but need to end the relationship so 'cheating' doesn't cause more stress than it solves.
- underlying insecurities you thought would be resolved by a relationship haven't been resolved by a relationship so are just coming back.

All depends how you use your lonely time.
If you just sit there and cry, yea that is not healthy, but if you actually use the time to better yourself or learn something or start a project or help someone in need or even volunteer for things in the community then loneliness can be bearable and also the source to learn about yourself.
I'm not lonely the majority of the time so I can only guess.

Loneliness is just a choice.

We rarely agree and yet I totally agree here.

I do think at times we get lonely and it is up to us to do something about it.