Requesting Disability Assistance At Airport

This may seem like a weird question, but I’m not sure what to do. I have Lupus, which causes me to have excruciating pain at times (especially joint pain when I’m unable to move positions). I’ve traveled all over and never needed to request assistance for anything. I’m okay (mostly) walking the very, very long (I complain a lot, and I stop sometimes) ways to the boarding gates and to the outside of airports. But I’m not okay standing in line for 2+ hours at time. It’s never been a problem before. But I’ll be landing in Lisbon (mid-morning) next month, and I’m honestly afraid of getting an immigration line that is hours lone and having nowhere I can sit. My body literally cannot handle that. So I started thinking about requesting assistance so I’d be able to wait in a wheelchair, I’d have a seat. But it feels *weird* and *wrong* because I don’t look sick. I’m young, and although a little overweight, I look perfectly fit. But I am sick, and I have all the medical notes to prove it. The last few times I’ve had to wait in long lines, I’ve had to be taken away somewhere else to sit or lie down, because, besides everything else, I start overheating and getting sick. But I feel immigration at an airport is not a place people would just pull you out of line and help because you’re in pain or sick, so I was thinking of asking assistance beforehand. But I still feel weird about it. Even as I type this I know I’m overexplaining this when I legally have the right to it. I’m just… not sure what to do. Help if someone’s been in a similar situation where they are fully mobile but certain situations can trigger horrible pain and requested help would be appreciated.

EDITED TO THANK EVERYONE: Thank you everyone for the kind responses and the support. I feel better about this now. I will contact the airline and will ask for airport assistance without guilt. Thank you for sharing your expetiences and making me feel better about it! ✨✨