Root canal(s) needed?

[sara777]

OK, after a routine checkup, my dentist discovers some very old fillings could use replacing.  The teeth were not bothering me at this point.  She replaces the fillings, on one she discovers a crack so she says I'll need a crown (my first one!) and that a root canal may be needed because the filling is deep.  After the fillings (before the crown) I start getting a lot of tooth ache on one of the teeth with the replacement filling.  It's not at biting, more just a prolonged pain that responds well to ibuprofen.  I don't mention it at the fitting of the temporary crown on the other tooth because I think it's just irritated from being worked on before and it will settle down.  By the time I'm back to get my permanent crown, I mention the pain to my dentist.  X-rays show nothing but that the filling is somewhat near the nerve and that my sinuses were cloudy.  She gives my antibiotics and says if that doesn't work THAT tooth will need RCT and a crown, too.  Now, 5 days later, the aching in that tooth has lessened.  My new permanent crown has no general pain but pain on chewing.  I sure that it's high, especially in the center.  I can't even chew on that side.  Would the height be enough to cause the pain?  Otherwise, it's fine.  I'm just wondering if out of seemingly nowhere I'm now looking at 2 RCTs and another crown.  It's 2 different kinds of pain...what will happen if I try to let it play out a little?  I don't want to jump into RCTs if there's a chance things will calm down on their own.  I also worry that there may be a trigeminal nerve issue at work here...I have headaches, etc.  I may clench my teeth and am wondering if an NTI bite guard will help the pain in those teeth.
Any advice is appreciated.