Need Opinions Please!!!

Hi, I've been trying to get pregnant for over a year now. My period has been on time every month, sometimes late but never more than a week. My period this month was set for March 18 (Saturday) but I ended up spotting light on March 17 (Friday) it started off light and brown then later got red and heavier with little cramping. Then on Saturday it was light. On Sunday there was hardly anything, didn't need a tampon. And today I haven't used a tampon there is no bleeding. Now normally my period is heavy 4/5 days. So this is really strange, has never happened before. Could this be implantation bleeding? When should I test? I'd really love any opinions. Thank You!