  We present a comprehensive timing and spectral analysis of the HMXB 4U
1538-522 by using the Nuclear Spectroscopic Telescope Array (NuSTAR)
observatory data. Using three archived observations made between 2019 and 2021,
we have detected $\sim $ 526 s coherent pulsations up to 60 keV. We have found
an instantaneous spin-down rate of $\dot{P} = 6.6_{-6.0}^{+2.4} \times 10^{-6}$
s s$^{-1}$ during the first observation. The pulse profiles had a double peaked
structure consisting of a broad primary peak and an energy dependent, weak
secondary peak. We have also analysed the long-term spin-period evolution of 4U
1538-522 from data spanning more than four decades, including the data from
Fermi/GBM. Based on the recent spin trends, we have found that the third torque
reversal in 4U 1538-522 happened around MJD 58800. The source is currently
spinning up with $\dot{P} = -1.9(1) \times 10^{-9}$ s s$^{-1}$. We also report
a periodic fluctuation in the spin-period of 4U 1538-522. The broad-band
persistent spectra can be described with a blackbody component and either
powerlaw or Comptonization component along with a Fe K$_{\alpha}$ line at 6.4
keV and a cyclotron absorption feature around 22 keV. We have also found a
relatively weak absorption feature around 27 keV in the persistent spectra of
4U 1538-522 in all three observations. We have estimated a magnetic field
strength of $1.84_{-0.06}^{+0.04} (1+z) \times 10^{12}$ and
$2.33_{-0.24}^{+0.15} (1+z) \times 10^{12}$ G for the two features,
respectively.
