That's fairly typical of my experiences as well. The book I would recommend reading is "Ask Your Guides" by Sonia Choquette. She explains a lot of the spirit guides in a general enough fashion that is easy to understand.
I too have plenty of spirit guides - three singular and one group to my knowledge:
- Don, who's a helper guide assisting me in this life
- A Native American guide, I have an idea what he's here for but it's very vague
- A falcon, who is there to assist me with its qualities
- The Three Sisters, of which I knew them before. Not sure where, but I was a fourth sister
I also seem to be able to call on other guides as needed with a little help:
- Money, who gives financial nudges (Slade Roberson writes about him a lot)
- Guru, who seems to be an ancient/former Yogi assisting me with my yoga practice as much as he/she can
- Runner guides, who as Sonia explains, can assist in logistical matters
So it's definitely possible to have multiple spirit guides. I believe most people do have multiples or time-share; it's just that one or two tend to come out more than the others.