In response to your original question, yes you can be friends with your ex.

Don't worry about that now though as "friend" covers a whole lot of territory; anything from friend with benefits to very close personal friend that you trust with your deepest feelings to that friend that you occasionally cross paths with but otherwise they aren't a significant part of your life.

Right now your focus needs to be on the immediate situation and the only person you truly have to be sure who's emotional well being is being taken care of. That person is you. What becomes of the relationship is secondary at this moment.

You seem very conflicted about this relationship and still have a strong emotional involvement in it. Just look at your screen name. Your whole identity is defined by someone else, i.e. mark. You call him your ex boyfriend but hold on to hopes that you will be back together again. You say it's over but still want him in your life. I don't think couples therapy is what you should be pursuing right now. You're not sure where you really stand so you need to first get a clearer view on where you are and where you want to be. If you don't know where you are then you can't even begin to approach the relationship.

I suggest you see a therapist on your own, and he do the same if he's so inclined as it sounds like he also has mixed feelings. Once you have a better focus of what direction you want to be heading in, then couples therapy may be an option if you both feel it would be helpful in resolving the relationship, whichever way it goes.

It hurts, you're unsure what to do, you're searching within yourself to place blame. Take a few steps back to get a better perspective of the situation. Do what you need to do to make sure you are not stuck floating in uncertainty.

I offer this advice not in criticism but with hope that the knowledge that comes with age (I'm probably old enough to be your dad) and the battle scars accumulated over the years will be of help to you.

Be well.