A dull intermittent pain on the left side of my chest, towards the underarm, that pulsates, almost to the rhythm of my heart: heart problems, attack?

Heart attack?: I don't know anything about your medical history to help my clinical judgement here. Women do gave heart attacks and they are missed too often. If you have diabetes or "pre-diabetes", or a family history of heart attack or stroke, I would especially have a low threshold for being evaluated. If you are worried about a heart attack, you should go to the ER for evaluation. Best wishes!

Left sided chest : pain with pulsing sensation should be checked; howver, this is not a heart attack until proven positive with blood or EKG findings.Not sure about your libido context? Definitely get checked.