Hi.

I have only used Cannabis once. I ate it, and in fact I ate too much. I experienced many negative effects similar to those listed in your original post. I have not used it since.

I think you should tend towards the theory that the new Cannabis was not laced (that is quite unlikely), but in fact it was much more potent and/or a Sativa strain.

I think it was just an overdose/bad trip. You can look at erowid.org and see that all those effects can be because of cannabis.