MrsN it is completely normal to have times where you feel like this, but I assure you, you are doing a great job
You and everyday life are perfectly good stimulation at the moment - even a brief trip out in the pram or the sling is utter fascination for them! If he gets upset left on his playmat then he probably just wants a cuddle/food/to have a moan - I think 2 months is probably too early to be getting bored 
And you don't need to talk to them all the time! It is great interaction, but you are allowed a break. Others may not agree with me, but I think (as long as they are happy, obviously not if it upsets them) it is a good thing to allow them time on their own to look and explore their environment. They need downtime too, the world can be pretty overwhelming when you are tiny.
I've been feeling the same this week - at 6.5 months, DS seems to getting frustrated that he can't move/do much, as his brain is a bit more developed than his motor skills. I was in tears on the phone the other day to my friend as I didn't know what to do with him anymore - she was very reassuring and suggested lots of simple things like bubbles, things that make noise (scrunchy paper, etc). Today I thought, ok, maybe I'm not as good as I thought I would be at interacting/playing with him (it seems like other mums find it really easy), but I know I show him how much I love him with lots of kisses and cuddles, which has got to be good, right? er, forgetting the really bad nights where he wakes up screaming every two hours and I yell at him to shut up
Sorry, dreadful load of waffle there. Summary: you are not alone, it is normal to feel like that, but have a big ((hug)) and remind yourself that actually you are a great mum 