It sounds like you may
have found the lower world. To be sure, when you try to journey again, you don't necessarily have to use a cave. You can use any piece of land to visualize yourself going into the Earth. Some use the bottom of a tree, some use cracks in stone or whatever suits you. Whatever you choose, it is wise to visual a piece of land you feel a connection to.
Next, the first thing you would do is make an intention. If you are going into the lower world for the first time you could have your intention being something like "I want to go into the lower world to find and meet my animal spirit animal guide." Your intention is VERY important in journeying. Be very clear. State your intention 3 times and then visualize yourself going into the Earth and visualize a tunnel going into the Earth. Just sense your self going down into this tunnel until you stop and you see something else.
Once you are in a ''place', look around. You may see nothing or you may just sense things. When you see or sense something ask if it is your guide. You may or may not get an answer. You will want to see the animal (or it's parts--I saw an eye first and then a leg, etc) 3-4 times and then ask again if this is your spirit guide. Wait for the answer that this animal is your guide (which could be a clear yes sound or some other sign- mine winked at me). It can be anything. Remember that your guide's power has nothing to do with its size- so if you get a mouse, don't be disappointed.
After you are done or the call back comes; thank the spirits you have come into contact with. Then visualize yourself leaving the lower world the same way you came in. Once out of the tunnel and seeing the Earth from the spot you entered, visualize your feet on the ground and see the Earth around you. This is to make sure you are fully out of the lower world. (If you do not do this, you could get agitated or have a headache or feel disoriented).
If you are feeling agitated or restless after doing a journey, make sure you have come out fully. You can always go back and leave again. If you have fully left the lower world, try going outside and putting your hands on the Earth and ask that the energy be released into the ground. Or ground yourself in anyway you that works for you. This is common when learning to journey since you are in touch with energy at a new level and the body has to process the shift.
Many times when one starts to journey things are fuzzy or out of focus. The more you journey the clearer things will become and the more you will "see." Things will also shift and change as you journey more.
Try not to worry about doing this wrong. Explore and ask questions when you meet your guide(s). Always have an intention when you go in and thank the spririts you come into contact with when you leave.
I highly recommend Sandra Ingerman's The Beginner's Guide to Shamanic Journeying. She is a student of Harner's and this book is written very clearly and it comes with a CD too.
Hope this helps.Good luck!