As the other attorneys say, you have the option of admitting you comitted teh crimes and serving the sentence, or taking the case to trial. If you had an attorney it woudl help you get the DA to discuss a plea because the threat of going and possibly losing will motivate them to discuss a plea. If you're on your own, the DA doesn't ahve a real threat because a trial is too complicated without proper training.
It's rare that a prosecutor won't make some sort of plea offer, no matter how serious the charge. Of course, depending on the charge and what the possible exposure is, any offer may be a non-issue. For example, if the charge is murder, it's a life sentence if you plead guilty, so an offer to plead guilty is a life offer. That would probably result in a trial since the stakes are too high.
A judge can't stop you from pleading guilty though - the judge can offer a plea deal, even over the prosecution's objection. While the DA can dismiss or change charges in a plea bargain, the judge typically doesn't, but instead can offer a better sentence if they wish.