A year ago I had a severe tooth abscess. Then a year later I had 2 bouts of cellulitis 3 months apart from eachother in leg. Why the weird infections?

Not sure. I am not sure, but if the tooth abscess was not properly resolved, the residual pathogens in the bone may have been involved. Typically unresolved infection does not affect or drain to the leg. Mandibular infections do drain to the lymph nodes and breast. There, is however, a commonality of pathogens in the body, potentially affecting both the tooth and a focus in the leg.
Have annual physical. Problems don't get better unless you are in charge of resolving them. When was last time you have seen your doctor or dentist prior to these infections? I recommend annual comprehensive physical exam with your medical doctor and see your dentist every 6 months. I think having healthy smile, healthy body, healthy mind are the keys to one's success in life. .
More info needed... How was the tooth abscess treated... extraction or root canal therapy? Any other medical conditions or medications? The dental infection should not have spread to your leg, especially a year later. A complete physical with blood work is in order.