I’ve told a few people since my diagnosis last November, and now I wish I hadn’t. I won’t go into my situation, but I’ve found only my husband and mom to be supportive. For some reason, I’m surrounded by people who either don’t know what to say, how to react, or simply think it can’t be true and must be wrong, and I need to not accept it. I usually don’t mention this, but since you brought up the EXACT same thing, I will go there-----I, too, get told I look fine, so how could it be “that bad”.
I was having a moment the other day. My 11-yr old son walked in on me while I was very upset. He asked what was wrong, and he already knew me and my knees were having a really hard day. I said I just don’t get why everyone thinks my life is perfect and NOTHING could POSSIBLY be wrong . …He looked at me and said in that way which only kids can pull off-- “Mom, you always have a smile on your face. You’re always so happy and nice. You’re not fat. Maybe they think your life is perfect.”
I laughed and said “So I guess I’m supposed to go around complaining all the time and gain 30 lbs, right?!” He shrugged and said “Maybe!!” 
So yeah—whether you tell or not, I wish you the best and hope you have a good support system. I’m trying to decide if I need to stop acting so “fine” all of the time. I should add, too, that all I really have is a probable diagnosis of Undifferentiated inflammatory arthritis, with PsA being the likely one (though I don’t have psoriasis).
–Lisa