Run for the hills. Immediately.

It sounds like an unhealthy relationship dynamic based on the words you have shared.... I think you could enjoy spending time with others WITHOUT the rollercoasters... it is not like good times are limited to him and nobody else..... just be careful you have not fallen into a codependent relationship with him! Take this time apart from him to be introspective and honestly reflect on why you stay with him.

"Experts say it's a pattern of behavior in which you find yourself dependent on approval from someone else for your self-worth and identity....Some research suggests that people who have parents who emotionally abused or neglected them in their teens are more likely to enter codependent relationships"

Consult these resources to help: [psychcentral.com]

[webmd.com]

Look up the term "stonewalling" as it pertains to malignant narcissism. If the situations/circumstances seem very familiar to you, run. Run like the wind.

Sounds like a dud relationship to me. Sorry, but to have a good relationship you MUST have open and honest communication and if neither one of you are on each others list of people to call if you are in the hospital, then I don't know what this is, but a solid loving relationship it is not.
If you like his company and enjoy just having fun from time to time then carry on, but do not expect anything to change from what it is today.

Three years is a long time to figure out what is going on. I understand that a person is not necessarily a a tosser just because he has some issues, but there needs to be some clear communication. It also almost sounds as if you are not sure what you want from him. I would first decide that and then communicate it to him. If you want him to be more invested, then let him know and ask if he is willing to give you that. In one comment you mentioned that you weren't certain he knew he was hurting you. If you are hurt, you need to let him know.

After three years, it is time to shit or get off the pot.

You deserve better than this. You can do better than this.

I know how hard it is to find someone who deserves you - I haven't been able to. The world is lonely and cold without intimacy or warmth. Even a tormentor seems better sometimes. It makes it harder to find someone else when you're dealing with the stress of a bad relationship. But please try - and keep your eyes open.

This erratic behaviour is not good for your health and I think the sensible thing would be to cut him off. I think it sounds to me that he has mental health issues ...this all or nothing pendulum is a familiar pattern for those who are on the bipolar spectrum. What you really need in a partner is someone who is consistent and reliable and who will steady you from the rollercoaster which you admit your life has been on for some time. No matter how good the good times feel, when they are followed inevitably by the uncertainties of not hearing from him and his unresponsiveness, this pattern of behaviour is doing you harm and your first duty has to be to taking care of yourself.

When you say "radio silence" you mean no contact unless he shows up to be "serviced"?
You Have your answer!

Hey Es..I would say your sometimes guy is probably not in your best interest. We all benefit from stability and consistency in a relationship..but being consistently on the 'coaster isn't a healthy way to spend your emotional energy. Considering all that you have going on I suggest moving on and giving someone new a try. I would love to have your options in that regard.lol

Without more info that comes off as dismissive of your problems, not caring much about your wellbeing. How long is this "radio silence"? I'm a loner and I appreciate someone needing space but more than a couple days or a week on a regular basis when you are trying multiple times seems very disrespectful- or a sign that they don't want a relationship.

Also the type that are dismissive of mental health issues and other health issues usually come off bulliysh to me.

Sorry but from what you wrote your "rollercoaster" guy sounds like a dud or possibly a manipulative abusive type.

I would say if this person hasn't responded in a week its OK to explore other offers. Let them know.the next time you see them...

You do deserve to be with someone who won't literally completely ignore you and your needs and belittle your health concerns. Thats not too much to ask.

If he can't accept it good riddance I have some issues too but they are resolving, you accept the person for who they are. It's the saying don't look a gift horse in the mouth, either you care or you don't accept someone for who they are they should be glad you like them