SP500- Bulls MUST hold 4070-4100 zone

Last week was a very good week for SP500, with the index reversing strongly and rising back above 4k important figure.
However, after reaching 4.2k, SP500 has started to drop and now is trading at 4120.
It remains to be seen if this is just a correction for the previous leg up or a resumption of the downtrend, but one thing is clear for me: for SP to remain bullish it needs to stay above 4070, if not, a new visit to previous low is very probable.
Although at this moment I don't have an open trade on SP500, my opinion is that the downtrend is not yet done and we will have a new low around 3.5k in the medium term.
I will become bullish if the index manages to get back above 4.3k