I did not include all undergraduate schools in the university I graduated from. Have I lost my chance at ever applying to graduate school? I've been really looking forward to the idea of returning back to school to complete my higher studies in a field that's both similar to my undergraduate degree, and the nature of my work. There are a couple of graduate schools I am interested in, located in Canada and in the UK, now I graduated from the United States. The university I graduated from contains transfer credits from another college I attended, but in total I attended 2 colleges (one is included in the transcript) and one community college.

The college and community college I attended were roughly 11 years ago, I rarely attended the classes in those two schools, and I took some time off to travel and work before I made the commitment of going back to school. I graduated with an undergraduate degree 2 years ago in a science-related field with a GPA of 3.8, and I still maintain a great relationship with most of my professors from my program.

It seems that I've made a grave mistake by not including my entire academic history when I applied to my last undergraduate university, should I forget about graduate school? 

*Edit

@NateEldredge That's brilliant. I took classes at College A and CC B, I traveled and worked for a couple of years and enrolled in College C. I then decided to move back to the United States, and applied to College D with only College C mentioned as my academic history. Now I'm thinking of applying to a graduate program, using the degree I earned from College D, with the included transcript from College C. Whew. 

*Further Clarification
Sorry. I'm not thinking all that clearly right now. I am worried that by applying to the graduate programs my full academic history will come to light, I did not mention the other schools in the application from the university I graduated from. By omitting them from the university I actually graduated from, I will be omitting them in the application to the graduate programs. Maybe it's my older age, but I feel like this is ethically reprehensible. Now I'm thinking of contacting my undergraduate university and explaining my full history, I'm afraid they will revoke my undergraduate degree.

Around 11 years ago I graduated from high school, I went to straight to a university. I never attended class, I eventually went to a community college, and I found myself in the same situation. I realized then, I needed to leave the environment I was in. I traveled, and worked for a couple of years. I eventually decided to go back to school, and started fresh at an international university in the country I was working in at the time. From there, I transferred to a university in the United States, and only mentioned the last university I attended and did not mention any of the other schools I attended.
On the basis of your "further clarification", I suppose that your grades at A and B were bad and that's why you mentioned only C when applying to D.  Now, when you apply to graduate school, you will probably be asked, as part of the application, to provide information about (and probably transcripts from) all the undergraduate institutions you ever attended.  If you're asked that, then you should honestly include all of A, B, C, and D.  You should explain the situation, emphasizing that (if I correctly understood your "further clarification") you became much more mature between B and C, and that therefore your record at A and B has become irrelevant.  (You should explain this so clearly that there will be no need for a clarification and further clarification.)