Just wondering if I'm having spasms. I KNOW I have a fissure...maybe more than one. I also have this throbbing ache. It aches in my tailbone. Sometimes there is a sharp stabbing pain. Sometimes I can feel my heartbeat in my anus, like in even minute localized areas. Sometimes it feels like "worms" or "little bugs" crawling in there when I feel the throbbing in pinpointed localized areas. Are all of these symtpoms spasms? If so, does the fissure cause the spasms and if yes, WHY does it do that?

Different people describe spasms in different ways, but generally speaking the severe pain of a fissure is being caused by the muscle spasm as it pulls on the wound edges of the fissure. Everything you are describing could be related to spasms and the concurrent stress on the nerves from the muscles tightening.
The reason fissures cause this problem is because the body is trying to be protective of a wound by drawing the muscle around it to protect it. The body doesn't understand it is making matters worse. It's just responding to the wound.

I would describe the pain like being cut open and then something poured into the wound. Mine have been severe, with pain lasting 12 hours yesterday and 8 today. Yesterday the pain was so bad I was in tears.
My doctor says the pain comes not from the tear but from the muscle spasm, so he has prescribed glyceryl trinitrate. According to him the only pain you feel from the tear is when you goto the toilet.

its true - the pain comes from the sphincter muscle spasm, the fissure causes the muscles to tighten up, the body thinks it's protecting itself...follow the advice of diet and take the trinitrate from the doc. The spasm will lessen over time. Hang in there.