Bam Margera says he's sworn off drinking on the heels of several concerning incidents in his personal life ... stating he's also tested clean for meth, after his brother accused him of being hooked on the dangerous substance.

Bam put out a series of statements Friday, first saying, "Well my brother made false accusations of me being on meth. But when I wear to god and Phoenix the wolfs life I’m not, I went with my lawyers to urgent care. Guess what Jesse margera. The results are negative. Now you will be evicted from castlebam sooner than later. Get your f***in s*** out HOMOner. Oh wait… not no more"

Jess accused Bam of being on meth and hallucinating earlier in the week when he was still on the run from cops ... a claim that's clearly gotten under Bam's skin. Bam denied these allegations and threatened to sue him for defamation and evict Jess from his home.

Bam also says for the sake of his son, Phoenix, he's done drinking, saying, "I have been through official termoil with my family."

What's more ... he praises his current girlfriend, Jessica, for having his back through his recent drama, saying, "For once I am not dating a hot dog strutting floozy." Also praising Jessica for helping him retain attorney Michael van der Veen in helping him with his ongoing case with his brother.

Finally, Bam takes a shot at his ex-wife, Missy Margera, who he believes tried to help the cops in finding him when he was on the run this past week.

As we reported, Bam turned himself in Thursday after 4 days on the run from the cops after his brother claimed Bam not only assaulted him, but threatened to shoot him dead.