I haven't had any problems in the past with achieving orgasm when on an SSRI. It doesn't mean that it's not a side-effect (even an undocumented one). You should discuss this with your practitioner and ask if you could be placed on a lower dose or a different medication. Always discuss changing medications with your physician and don't lower or stop anything on your own. These medications, stopped or changed abruptly, without the direction/advice of your physician, can cause horrible side effects, including/especially withdrawal symptoms:

headache, vomiting, diarrhea, nausea, loss of appetite, increased anxiety/depression, insomnia, fatigue, dizziness, etc.

Is NO GOOD. Talk to your doctor.