Pregnant on the implanon?

Patient: Ive had the implanon rod in for about 1 and a half years, my partner and i have been together for more than 3 years. its only been in the last 3 months that we havent been using condoms, and im concerned about being pregnant. i know there’s a very slim chance, but thats still a chance. and i was wondering if i did a pregnancy test if the test would be altered whether or not i was, because of the implanon? and also if i would have to get it out asap? i would regularly get a period every 4 months that would last for about 4 weeks, would there be a possibility of more than one egg then? i already have a toddler and im getting the same symptoms as i did with her, yet i havent had anything like this the rest of the time ive had the implanon in. help!