Stuttering

My son who is 4 yrs and 3 months old has a history of stammering for last two years. He first started when he was 2.5 years. It continued for 3 months and then disappeared. It again started when he was 3, continued for 1 month and disappeared. This time it started around one year back and presently it is at its peak. He drags for seconds on the first letter of a word. And now he stammers on almost every second word. But amazingly the stammering is not consistent. He pronounces the same word correctly in some different sentence. In fact this characteristic was there in earlier two episodes also. We are blessed with one more son in May last year and it (the third episode) started sometime after that. The child specialist says that this may be due to attention that his younger sibling is getting. But then what was the reason for earlier two occurrences? He also suggested us to wait for some more time .Some more points I would like to add that he is very very active and talkative also. He hardly sits, except when he is watching his favorite cartoon. He is very bright and has got a very sharp memory (I am not saying this as a parent, but his teacher has also noticed this).He started solving jig saw puzzles at an age of 2.5 yrs.Kindly suggest what should I do? Recently we went to see a speech therapist. Although he (my son) did not cooperate much but whatever he spoke he did not stammer at all in his (speech therapist’s) presence. He only advised us to give him more attention. He completely ruled out that it is an ADHD case. We are totally confused and don’t know what to do. Should we intervene at this stage or wait to get it over by itself as in earlier cases?Can it be treated by stramonium 200?