I just want to go fishing like I use to but what if my bag leaks why I'm fishing and far from home. Or it falls off like it has the last 3 days. I just got all these playing thru my head.
What's the worst that could happen? On your first times out, don't go to a formal dinner or job interview, obviously, but if you go fishing - would you normally go with someone who knows about your stoma or who you think you could tell about it? If you get a leak... well you ruin some clothes (wear old ones you don't care about). If your clothes get in a mess and strangers look at you funny, tell them you slipped over in a cow-pat or something.
You will also find that you get much more skilled at changing the bag over time, and will learn to be able to deal with leaks more quickly. For example, I can now change my bag without undressing at all - I just tuck some pads or paper towels into my knickers to protect my clothes, and lift up my dress or t-shirt and tuck it under my chin (or pin it up with a clothes-peg). I can usually do this without getting in a mess at all, so if I had a leak while out I would just find the nearest bathroom and do it there. Keep a complete change of clothes with you as a back-up just in case.
Also think about babies and toddlers, and how you deal with their bathroom needs when out (if you've any experience of that) - you learn what you need to take with you, e.g. change of clothes for emergencies, changing things. When they need changing you find a bathroom. No one thinks babies are gross if they get their clothes dirty or have an accident. It's only that we've been socially conditioned to think it's terribly embarrassing for adults, but in fact we can and should treat our stomas as we would treat a small child going through toilet training. Yes it's mucky at times, but it's also unavoidable, and really not so very big a deal in the scheme of things.
I've also found that no one's opinion of me has changed since I've had my stoma. And yes, when I have had leaks, my mum has had to help me clean up - she doesn't care. Some people may care, but there are also plenty who don't. Do you have anyone close around to help you and give you some confidence in going out?