I am going out with friends - I need advice

A little background information: In January my phobia took a turn and since then it's got to the point that I now really struggle to leave the house in case I am sick. Even a 20 min walk around my area elicits very bad panic episodes; I become unable to breathe, everything becomes very bright, my whole body feels numb, and I have to sit on the ground until it passes because I become unable to walk. Walking to places is fine, the walk back and realising how far I am away from home is when that happens. When I go shopping, I can only go out for 1hr - 2hr before I start to feel very unwell.

I haven't seen my friends in 5 months, some even longer. We are all going out for the day, roughly from 12pm-9pm. We will watch a 3hr movie (I have a really bad fear of cinemas because of feeling trapped, the level of sound and size of the screen always makes me feel so nauseous, almost like motion sickness, and this fear on top of my fear of going out is too much to handle), and walk around. I feel bad cancelling but I have no idea how to get through the day. I hate to admit that I'm dreading it. Even if I'm not ill, the anxiety makes me feel so unwell, consequently, it makes me lose every ounce of energy in me, I'm worried I'll become stuck in the situation.

I'm really stressing. It's on Monday. I really don't know what to do, I don't want to disappoint anyone but this so far out of my comfort zone. I tried talking to my friend about my fear but she doesn't understand.

I just feel like crying