If you are barely hitting the repeater, then those that could not hear you whilst the host could hear you probably just did not have the ability to discern you voice from the static as well as the host. Because you were on a repeater, other users squelch setting would not affect anything as the repeater is presumably hitting them with a good signal, it was just repeating a weak signal. Also - if you have a weak signal and your radio happens to be transmitting in NARROWband instead of WIDEBand, it would be even harder to make out your voice.. Also, always be sure you are speaking loudly and clearly with the mic no more than 1-2 inches from your noise-hole.
More power might help, but a better/bigger/higher antenna WILL help - upgrade antenna first, power second.
As for not hearing your own voice, try getting your test-radios at least 50 feet away and trying again.