Online Sportsbook taxes

I need some help determining how to report winnings from a single online Sportsbook. I won’t be receiving any documents and actually ended the year in the red. I bet very minimal amounts but was wagering like $10 a game on 3 NBA games a night with maybe a football game too. Most would lose but a few would win and I basically just kept the money in and replayed it, like when you win one spin on the slot and then lose the next. My question is, how to I report this?  It’s my understanding that you don’t simply report the net outcome for the year (which would be a loss, actually). If my understanding is correct, I can count the outcome of a “session” but I don’t know what would constitute a session for this. Is it a single day, one session per sport per day???  I appreciate any help.