You appear to be severely underestimating the risk associated with (a) investing with leverage; and (b) shorting stock. As well, you defend your actions by saying you 'agreed with the specialists', but keep in mind that there is never unanimous agreement over what will happen in the market, and even if someone knew with 75% certainty that a stock will go down, there is still a 25% chance it goes up instead.
Why does leverage increase risk?
Risk in finance is defined as the variance in possible returns. So if your possible return on being right is to double your money, and your possible risk on being wrong is to lose everything (like betting $5 on the flip of a coin), your risk is massive. If your possible return on a simple equity investment is 10% over the course of a year [a high-end estimate of a good stock market return], and your risk of being wrong is -10% over the year [which would be a devastating 1-year return], your variance in outcomes only goes from 90-110%, so you your risk is lower.
But when you borrow money to make that lower-risk investment, look what happens: Assume you invest $50 of your own money, and $50 borrowed money. If the stock goes up 10%, your investment portfolio is worth $110. Because you only used $50 of your own money, your net equity earnings are $10 / $50 = 20%. ie: you have doubled your rate of return from 10% to 20%. If you like, you could immediately pay off your $50 loan and be left with $60, which again shows the 20% earnings. Now assume the same scenario, but the stock drops by 10%. Your total portfolio drops to $90, a loss of $10 off of your $50 personal cash invested (ie: a 20% loss). So the variance in possible return has moved from 90%-110%, to 80%-120%. Your risk has effectively doubled, because half of your investment comes from borrowings.
Now imagine you had 5x leverage, meaning $1 equity for every $5 of borrowed funds. So if you invested $600 in the market, and it dropped by 10%, you would go down to $540 in value. But you would still owe $500! So you will have dropped your $100 equity value down to $40, meaning you would turn a 10% market loss into a 60% personal investment loss!
And every day you wait for the market to recover [which is not guaranteed to happen, particular in a short enough time frame that you can rely on it like this], you have to pay interest costs, meaning at say 5% interest annually, you might add another $25 / year in interest costs, or about $2 / month (which is 2/ 40 = 8% of your current $40 equity value, being lost every month to interest!).
As well, keep in mind that when shorting stock, your risk is technically unlimited - if a $5 stock goes to $15, you will have lost 200% of your original investment value, a risk capped at 100% when traditionally buying stock.
The more you combine these risky strategies, the more your risk increases, it should come as no surprise.
(I did not comment on the margin-call aspect of this, which Freiheit includes in his answer. In short, if your equity drops down so significantly, you likely would need to repay your loans to your broker, whether you want to sell or not.)