Could tiredness, nausea, unexplained bruising, heavy long lasting periods, & recurrent canker sores 3 mos postpartum indicate low iron ?

Could be but...: It is hard to say without a thorough history and exam, maybe some testing- blood, thyroid, etc. Three months postpartum may seem like a life-time for you. Your habits, nutrition, sleep patterns, hormones, stress may still be playing a major factor on your immune system. Get to a Dr. and be evaluate asap

Yes...: Postpartum long periods of bleeding leads to loss of blood and low iron - low hemoglobin: Iron def anemia,It may associated B12 def also. Low HB Low oxygen heart work hard. This all will results in tiredness, pale color, palpitations, weakness, short of breath, nausea ? and canker sores, You should get checked by your PCP and GYN and treated for anemia, prolonged bleeding which is causing gthis