I need your help is the following:

My Model is as the following

Dependent variable is GDP per capita growth rate

Explanatory variables are

Domestic Investment (measured in Capital formation as percentage of GDP)

Population Growth

Human Capital (Measured in enrollment in secondary education)

FDI (Measured in Inward FDI)

Openness (Measure in trade/Gdp)

The problem is that adjusted R-Squared is about 0.67 and significant while all explanatory variables are insignificant!

The data set is for one country over 20 years

Here are the results

Source | SS df MS Number of obs = 20

-------------+------------------------------ F( 6, 13) = 4.49

Model | 3.34868043 6 .558113405 Prob > F = 0.0112

Residual | 1.61568199 13 .12428323 R-squared = 0.6745

-------------+------------------------------ Adj R-squared = 0.5243

Total | 4.96436242 19 .261282232 Root MSE = .35254

------------------------------------------------------------------------------

lngdpgrowth | Coef. Std. Err. t P>|t| [95% Conf. Interval]

-------------+----------------------------------------------------------------

lnschool | .9458499 2.239839 0.42 0.680 -3.893028 5.784728

lnpopgrowth | -7.45615 3.887698 -1.92 0.077 -15.85501 .9427097

lninv | 1.322297 1.559077 0.85 0.412 -2.045884 4.690478

lnfdi | .1611782 .1894099 0.85 0.410 -.2480169 .5703733

lnbank | -2.87771 1.673274 -1.72 0.109 -6.492598 .7371791

lnopen | -2.226014 1.827137 -1.22 0.245 -6.173303 1.721275

_cons | 16.22721 9.14738 1.77 0.099 -3.5345 35.98892

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Breusch-Pagan / Cook-Weisberg test for heteroskedasticity

Ho: Constant variance

Variables: fitted values of lngdpgrowth

chi2(1) = 4.80

Prob > chi2 = 0.0285

. estat bgodfrey

Breusch-Godfrey LM test for autocorrelation

---------------------------------------------------------------------------

lags(p) | chi2 df Prob > chi2

-------------+-------------------------------------------------------------

1 | 0.072 1 0.7884

What should I do in this case?