Ferritin and supplements

Im dealing with low ferritin.. for awhile the iron supplements TRI FEREXX 150/mg along with vitamin c seemed to be helping. the last few months my iron has dropped again. My Canadian numbers were April20187 September 2018 33 April 2019 23 July 2019 29 September 201921 since APRIL to SEPT ive been really faithful about my supplements, drink iron water, eat pork liver, etc. and my tests are down, Has anyone had any luck trying different supplements or is it possible our bodies just arent absorbing? THANKS???