Ocrevus side effects?

Hi. I was diagnosed with relapsing remitting MS just over a year ago. I have been receivibg MS infusions since then, so i had my 1st 2 a few weeks apart one 6months later and then my most recent one. I seemed fine after the first ones but the day after my most recent one i have experienced really bad stomach cramps…having read possible side effects it does say this is one but lists it as serious and says i should speak to medical professional…this seems a bit drastic. Has anyone else experienced similar side effects?