I am very wary of assuming too much from the limited details you've given.
However, it sounds like your role is much closer to being a founder than a first employee. You're in before outside money/validation, so there is a huge risk that your equity will be worth nothing. Are you also the entire technical department from the start, and therefore the only person who is actually building the founders' big idea for now?
If that is the case, it sounds like you did not get a good deal at all. I would definitely take advice from someone independent, where you can share all the relevant details. If you want to renegotiate, doing it early might be possible, but doing it later is very unlikely.
However, it sounds like your role is much closer to being a founder than a first employee. You're in before outside money/validation, so there is a huge risk that your equity will be worth nothing. Are you also the entire technical department from the start, and therefore the only person who is actually building the founders' big idea for now?
If that is the case, it sounds like you did not get a good deal at all. I would definitely take advice from someone independent, where you can share all the relevant details. If you want to renegotiate, doing it early might be possible, but doing it later is very unlikely.