Ditto on getting him to your pediatrician ASAP. If you have a concern, it's coming from somewhere, and often there is more to our gut feelings than just what we're able to verbalize or cognitively recognize. I have soooo much autism in my family (speech is the first to go), and it is SO IMPORTANT to catch it as soon as possible, that it isn't worth waiting till June, just in case. He's at prime time for autistic regression too (unfortunately).
I agree that many children just outgrow these stages of regression, but if it is more than that, you will always wish you paid the co-pay (or even the full amount) and got him checked out. Often times with boys their speech takes a dive while their large motor skills take a leap, so the others are correct that often they outgrow it, but still if it was my child I'd go in ASAP.
I would go so far as to specify with the doc that you are concerned about something like autism. When you specify things with your doc, they tend to take it a little more seriously and probe more deeply into what's going on, hence you get a more thorough exam time with the doc!