If I was you then I would lay off the clove oil. If necessary you could break a capsule into water and use it as a mouth wash if you need to but spit it out afterwards and do not swallow. Therefore do as your school friends probably once told you ;) lol
If you get some CS then you could use that as a mouth wash and swallow it to treat your stomach and with a bit of luck the giardia.
Is your tooth causing any problems? It is difficult for me to offer advise as I am not a dentist and I have no experience of root canals. Is there an infection? CS might fix it if you regularly mouth wash with it.
BTW I have updated my previous post so please read the bottom bit which I added.