B.S.
Pasco county has a great program for kids with expressive speech and language problems called the TALK program. It's a preschool class for kids with speech delays where kids go all day 2 or 3 days per week (depending on how severe their problems are) during the school year. I know that there is at least one TALK classroom in Port Richey (I dont' know what school it's at), there is one at Lake Myrtle Elementary in Land O Lakes, and another one is opening up at New River Elementary in Wesley Chapel. (I think that there are a few more, but those are the only ones that I know for sure about). It's an amazing program - my son has been in a TALk classroom for 1 1/2 years and has made tremendous progress (he has a rare nerve problem where he has trouble controlling his facial muscles so he has extreme articulation problems). Unfortunately, the program doesn't start until age 3 when children stop receiving benefits from Early Steps and get them from the school system instead.
How is your son during speech therapy? Does he respond well to the therapist? Sometimes the therapist themselves can be a problem - not that they aren't any good but if your child just doesn't gel with them then they won't make as much progress as they would otherwise. Also, it can take months after starting with a new therapist before you start to see any change, just because it can take that long for your child to bond with them and want to work with them, so don't give up hope yet. Has your therapist given you advice and activities to do in between sessions? If so, I know that it's hard but you've got to do them, and if not ask for some.
Remember that you know your child better than anyone in the world. If the doctors are talking about autism and you don't buy into it, get another opinion from another doctor, or ask what else they think that it might be and do some research of your own. Unfortunately, I have found that doctors are human, too, and they often don't know as much as they claim to. At the same time, you can't afford to ignore any possibility, no matter how scary, because early detection and treatment can make a huge difference with most disorders.
You said that your son was premature - does he have any other problems besides speech? You may want to have him evaluated by at OT and maybe a PT as well - we thought that my son was fine but he was compensating for some low muscle tone issues and developing some really bad (developmentally inappropriate) habits. Plus, a lot of kids respond better to speech therapy when they are receiving OT as well... A lot of therapy centers will give free evaluations, and the more information and opinions on your sons condition you have the better.