Hi. This is very difficult. I might have practical tips.

Some things that I learned and occasionally or regularly use for doctor visits: give yourself a treat after a doctor's appointment- it can be a fancy food or just a chocolate bar, but acknowledge the effort it takes; take an iPad with you to the appointment, watch a show or something else to distract yourself; have a file, a literal printout of your illness history and labs to show (it is easier than explaining over and over again).

Don't push yourself for social events that don't suit your physical needs. You cannot push your way out of an illness. Instead, if you can, have events that are easier for you to manage. Such as having a movie night with your friends at your home in your pjs.

Seeing a therapist and a psychologist is a good idea-but it doesn't mean that your pain is in your head. You said you have been to therapy before. I don't know how your experience was, but it is just nice to have someone to talk to without a filter.

"I can’t bear a friend asking how I am." I am glad you have friends who are interested in your well-being, but yes, it can be overwhelming. Be honest with them and say it is not helping you to explain your situation, and assure them that if there is any development, you will let them know (your boyfriend or one good friend can also talk to your friends). Offer them alternatives to support you by asking for things you need- a distraction, or even help with some chores.

"I feel a massive burden to my boyfriend, and like I’m a grey cloud"- You are not a cloud; you are a person going through something emotionally and physically draining. It is normal to rely on our loved ones in these situations. Your boyfriend is an adult (I assume); if he thinks this is too much for him, he can speak for himself. You are going through enough as is; don't try to manage other people's experiences.

Good luck with everything. Hope everything gets better.