What I am saying is I sold it the first time and bought again after which price dropped significantly. I am still hodling from the second attempt, how do i claim this thousands of dollar loss to offset the few hundred gain?
it sounds like you only sold once in 2018. based on that: when you sold, you realized a capital loss. that capital loss is reportable on schedule D of your tax return (up to $3000 maximum deduction).
you then bought back and held BTC. even though that position is in profit, you haven't sold as of 2019, so a taxable event hasn't occurred yet. the second trade shouldn't be reported on your 2018 return.
p.s. you might want to summarize your trading activity with dates just to make sure no is giving you inaccurate advice.