May very well be parasites, esp since you have mucous in BMs, could possibly be liver flukes...Often, when there is one kind there is others..
Not to worry, you can get rid of this, with Wormwood /bl.walnut/cloves it has worked for many... parasites are the "silent enemy"nowadays, and people just don't talk about it.
It may seem improbable(as in:I haven't traveled outside the US, I'm a clean person, I don't eat questionable foods,etc) , and often one will go into DENIAL, as this is not the easiest thing to face.
But, as soon as you see some results, you'll be encouraged to go on, and it'll certainly make a huge difference in the way you'll feel.
You may want to do some liver flushes, you'll see evidence of flukes if you do.
For the fullness and throbbing in the right side, you may want to use Castor Oil packs, they'll relieve the pain and fullness.
There are many different things you vcan use besides the Wormwood combo. Grapefruit seed extract, pumpkin seeds, cayenne, garlic, myrrh, oregano oil, olive leaf extract, wormseed, cascara sagrada, to name a few ...
Also, do liver flushes, Psyllium/Bentonite shakes(these will get the muciod plaque out, and since the parasites hide under the plaque, this will help in expelling stuff), bowel managementto cleanse the intestines and help with the constipation, you could also try coffee enemas, as they are very helpful in removing bile and detoxifying the system, esp if you get the headaches.
Take care... :)