Have you considered volunteering? It’s a great way to not only help others in need, but to feel good about yourself in doing so. As an introvert, it may be intimidating to put yourself out there in this way, but there are volunteer opportunities of all kinds that may not require intense social engagement but still expose you to some people and that purpose you are searching for.

Also, you don’t mention what kind of chronic disease you have (and by no means do you need to disclose this), but there may be opportunities to network with others who have the same disease (message boards, support groups, etc.) Perhaps speaking to others who have thrived despite the disease could be inspirational to you.

More than anything, I’d encourage you to be kind to yourself during this time. Ending a long-term relationship is a grieving process of sorts. It’s natural to feel down as you adjust to life without your partner. Even if you had an active social life, I suspect you’d still feel a sense of loneliness to some degree. You will get through it. Do things for yourself that make you feel good. You deserve it.

Best wishes to you.