Apes,
The one major thing I've learnt is that in the situation you describe above, do NOT continue to try to go, even if you feel you need to!! This is a tough one because there is such a sense of relief after having a BM that you just want it to happen and get it out of the way for a few hours! It was a big mistake for me because this is what prevents you from possibly healing more quickly & sets you back a little again.
Internal piles do not help at all because they can increase the rectal pressure and make you feel you need to go, especially if your bowels are more sensitive as mine are. They can also make you feel (when aggravated) that you haven't completely evacuated and then we get that urge to push a little more again after we've actually expelled all we need to at that time. It's really important to truly recognise your body and the sensations that go on in your bowels so you can determine when you do actually need to go properly. This isn't easy though but comes with time. As we cant physically see the internal hems, it's hard to judge the impact they have on our BM's & bottoms but they do have an impact! so just be aware of them.
I have read a lot about these urges and the sensation that your bottom feels like it's going to "fall out" after Botox and would say have a look for the Botox diaries - there are many and these might help reassure you that what you're going through is pretty normal stuff! :)