
Think of meds as just one weapon in your aresenal. They may help your son control his impulses, calm down, and focus better, but they won't teach him social skills. It sounds like his meds need to be re-evaluated and he needs to go through some behavioral therapy.
My son's school has a great counselor who works with kids on things like personal space, making friends, etc. in small groups and individually. The small groups keep the kids from feeling singled out and show them that they're not alone in this. There are also lots of psychologists and counselors who can help with this type of skill building.
On the play date topic...my son rarely gets invited to play dates either. I decided to take matters into my own hands and invite kids over to our house more often. It turns out that most parents are just too busy to follow through on their children's requests for playdates. The kids that come over say they've asked tons of times to play with my son and the parents confirm that they just haven't had time to put together play dates. Now, my son gets to play with his friends and their parents have a few hours of free time on the weekends.
I have the same type of son. He is now 12. He has been on concerta AND tenex since the start. They both work together like a charm! 
My son was at a much higher dose at age 7, 54mg &b 1 mg of tenex. He is at 90mg of concerta and still at 1 mg of tenex. I am about to increase with the agreement of his doctor this week.
Keep in mind, these are NOT weight or age based but by their success. AND my son metabolizes the meds quicky.
I suggest calling the doctor, try increasing his concerta and then try adding tenex, you can break them in half. Start with a .5 mg 
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I have so been in your shoes!! It really hurts us moms!!
And remember they have adhd, a neurological disorder, he can't control it!! This will help him!!

Keep doing such a great job being his mom!!