I am valued, but the startup is really low on money (because we try to get our project done, not do much client work). As some compromise I now do it just 3 days a week and partly remote.
I don't want to be too negative but I have been in a similar situation. Once money starts flowing it's very unlikely that you will get more. If you being underpaid and have no serious equity you are being disrespected and that won't change.