I don't have high 'bad' cholesterol but like you I don't have nearly enough 'good' cholesterol. Mentioned that to my heart doctor this week and told him my general practitioner had told me to take fish oil and eat a lot of fish, mostly Salmon.
My heart doctor told me that was fine but it probably wouldn't do much good.. 'good' cholesterol is genetic.
BTW... I first tried fish oil, taking it for a year or so... did nothing. THEN tried eating more fish, mostly Salmon... and doing so DID elevate my 'good' cholesterol, but very little. Today I still maintain the regular eating of fish, mostly salmon, in my diet but that's mostly because I like it... I no longer expect it to raise my good cholesterol much if at all.
About all the above, that's just me... fish oil may work for you and others. - JamesJM