You have a really IGNORANT Doctor and if possible - I'd not go back to someone who is so willing to give you not only bad advice, but wrong advice.
They are wriggling because they can now. They've learned a lot of new physical milestones and want to try it out! All the time!! It's normal.
The distraction and movement phase doesn't stop until about 3 years old - if you choose to continue thru it. Many Moms quit because they don't feel like doing it anymore, are afraid of biting (which is 100% able to be stopped!), or think that baby is too old.
Best thing to try is to nurse in shorter intervals, so he has more times to nurse. Also try being in a quiet and dim room - less movement and stimulation from environment is better.