Just had a endometrial ablation surgery last week and now I am having lower abdominal pains, why am I'm having these pains now
Jennie, you just had surgery. Literally your body has been rearranged a bit from what it was. That requires some healing.
That said, if the pain becomes extreme and/or you begin bleeding a lot, contact whoever did the ablation immediately.
Jennie ablation doesnt do much in the way of ridding you of your symtoms I'm afraid. Im really sorry to be the barer or bad news about that. Many women are under the impression it should help all their symtoms when in truth its pretty pointless. 
You need excision surgery for it to really take effect which cuts the tissue from the route of the problem as oppose to ablation which lasers off the top surface layer of the tissue and grows back pretty quick and sometimes worse than before. The excision surgery also needs to be done by an accredited Endo specialist for them to be able to get it all properly. If your from the UK this will be pretty rare to find but not completely impossible. Please ask your gyno or specialist why you werent given excision as this is the most successful treatment for endo and urge to see an actual accredited endo specialist. I can almost guarantee you gyno isn't accredited. Sorry your having to go through so much pain... good luck with your journey hun xx