Methotrexate

Marissa • 39 y/o. PCOS. Currently TTC #2 via IUI. It took 3 FETs to have baby #1.
My OBGYN is now recommending me to get a methotrexate injection due to her suspecting I have an ectopic pregnancy. In my area, the cancer center is the only place that can administer this injection. I met with them today and am scared of the possible side effects of this medication. I will be having this injection as soon as tomorrow and am scared, since it is used for cancer patients (even though I will be having a low dosage). Has anyone taken this medication? What can you tell me about it?