It all depends on the kind of blood you have in your stools. If it's a bright red, looks fresh, then it probably is something wrong with your rectum area. Are piles another word for hemmroids? Hemmroids can bleed and even rupture on occasion, but, for the most part, this is not a big deal and they're better left alone. Unfortunately both constipation and long periods of diarrhea (sitting on the toilet puts extra pressure on your rectum and your hemmroids) make them worse. If there's any way to limit the amount of time you spend on the toilet, and yet also limit the need to strain to pass the stool, then that will help them heal. You may want to look at suppositories, which also will help them heal. The other thing that causes a lot of bright red, fresh blood is a fissure in the rectum. I am under the impression that this is like a tear in the skin. They hurt a lot worse than hemmroids, but there's not a lot you can do about them either, except try to keep from straining or sitting on the toilet for long periods of time. I think you also have to be very careful about cleaning yourself after bowel movements to avoid infections.
If the blood is not bright red, but is dark red, brown or black, then you need to definitely get another colonscopy done, even if you have to see another doctor. Blood that is darker is coming from higher up in the intestinal tract or stomach, and indiates IBD or stomach ulcers, both of which need to be treated with medicine. IBDs can sometimes be hard to find because sometimes the inflammation is a lot higher up in the intestines than the scope can see, or the intestines are in a state of remission when the scope is performed.
Mucus is common with both IBS and IBD, so in and of itself it is not very telling. All of your other symptoms could also go either way. So really it's a matter of deciding where the blood is coming from. If bright red, it's from low down and is likely as your doctor says, nothing to be alarmed about. If dark red, it's coming from higher up and you need more testing.
Unfortunately, since you have both D and C, it makes it hard to treat your symptoms without giving you the exact opposite problem. Fiber is one thing that can help balance the two out. Also, you can try probiotics. The easiest thing to start out with is yogurt, then work your way up to the pills. They really help some people's D and C and gas problems. You should also look to take gas relief pills when you eat to see if you can help eliminate that gas pocket that you get later on down in your intestines. Peppermint tea is a favorite on here for gas relief as well, but you should not take it if you are prone to acid reflux/heartburn.