I have an equation in the aligned environment to align the equal signs together. However, the last equation is too long, and I want to break it up. When I insert a linebreak, all the equations above the last one shift to the right. The code:
\begin{equation}
\begin{aligned}
\log\left(p\left(s|\alpha\right)\right) & = \sum\limits_{i=1}^O\left(\log\left(\frac{1}{\prod\limits_{k=1}^K\Gamma\left(\hat{\mathcal{S}}_k^i+1\right)}\right) + \log\left(\frac{\Gamma\left(\alpha_0\right)}{\Gamma\left(\sum\limits_{k=1}^K\left(\hat{\mathcal{S}}_k^i+a_k\right)\right)}\right) + \log\left(\prod\limits_{k=1}^K \frac{\Gamma\left(\hat{\mathcal{S}}_k^i+\alpha_k\right)}{\Gamma\left(\alpha_k\right)}\right)\right) \\
&= \sum\limits_{i=1}^O\left(-\log\left(\prod\limits_{k=1}^K\Gamma\left(\hat{\mathcal{S}}_k^i+1\right)\right) + \log\left(\frac{\Gamma\left(\alpha_0\right)}{\Gamma\left(\sum\limits_{k=1}^K\left(\hat{\mathcal{S}}_k^i+a_k\right)\right)}\right) + \log\left(\prod\limits_{k=1}^K \frac{\Gamma\left(\hat{\mathcal{S}}_k^i+\alpha_k\right)}{\Gamma\left(\alpha_k\right)}\right)\right) \\
&= \sum\limits_{i=1}^O\left(\sum\limits_{k=1}^K\left(-\log\left(\Gamma\left(\hat{\mathcal{S}}_k^i+1\right)\right)\right) + \log\left(\frac{\Gamma\left(\alpha_0\right)}{\Gamma\left(\sum\limits_{k=1}^K\left(\hat{\mathcal{S}}_k^i+a_k\right)\right)}\right) + \log\left(\prod\limits_{k=1}^K \frac{\Gamma\left(\hat{\mathcal{S}}_k^i+\alpha_k\right)}{\Gamma\left(\alpha_k\right)}\right)\right) \\
&= \sum\limits_{i=1}^O\left(\sum\limits_{k=1}^K\left(-\log\left(\Gamma\left(\hat{\mathcal{S}}_k^i+1\right)\right)\right) + \log\left(\Gamma\left(\alpha_0\right)\right) -\log\left(\Gamma\left(\sum\limits_{k=1}^K\left(\hat{\mathcal{S}}_k^i+a_k\right)\right)\right) + \log\left(\prod\limits_{k=1}^K \frac{\Gamma\left(\hat{\mathcal{S}}_k^i+\alpha_k\right)}{\Gamma\left(\alpha_k\right)}\right)\right)
\end{aligned}
\end{equation}
What I want
\begin{equation}
\begin{aligned}
\log\left(p\left(s|\alpha\right)\right) & = \sum\limits_{i=1}^O\left(\log\left(\frac{1}{\prod\limits_{k=1}^K\Gamma\left(\hat{\mathcal{S}}_k^i+1\right)}\right) + \log\left(\frac{\Gamma\left(\alpha_0\right)}{\Gamma\left(\sum\limits_{k=1}^K\left(\hat{\mathcal{S}}_k^i+a_k\right)\right)}\right) + \log\left(\prod\limits_{k=1}^K \frac{\Gamma\left(\hat{\mathcal{S}}_k^i+\alpha_k\right)}{\Gamma\left(\alpha_k\right)}\right)\right) \\
&= \sum\limits_{i=1}^O\left(-\log\left(\prod\limits_{k=1}^K\Gamma\left(\hat{\mathcal{S}}_k^i+1\right)\right) + \log\left(\frac{\Gamma\left(\alpha_0\right)}{\Gamma\left(\sum\limits_{k=1}^K\left(\hat{\mathcal{S}}_k^i+a_k\right)\right)}\right) + \log\left(\prod\limits_{k=1}^K \frac{\Gamma\left(\hat{\mathcal{S}}_k^i+\alpha_k\right)}{\Gamma\left(\alpha_k\right)}\right)\right) \\
&= \sum\limits_{i=1}^O\left(\sum\limits_{k=1}^K\left(-\log\left(\Gamma\left(\hat{\mathcal{S}}_k^i+1\right)\right)\right) + \log\left(\frac{\Gamma\left(\alpha_0\right)}{\Gamma\left(\sum\limits_{k=1}^K\left(\hat{\mathcal{S}}_k^i+a_k\right)\right)}\right) + \log\left(\prod\limits_{k=1}^K \frac{\Gamma\left(\hat{\mathcal{S}}_k^i+\alpha_k\right)}{\Gamma\left(\alpha_k\right)}\right)\right) \\
&= \sum\limits_{i=1}^O\left(\sum\limits_{k=1}^K\left(-\log\left(\Gamma\left(\hat{\mathcal{S}}_k^i+1\right)\right)\right) + \log\left(\Gamma\left(\alpha_0\right)\right) -\log\left(\Gamma\left(\sum\limits_{k=1}^K\left(\hat{\mathcal{S}}_k^i+a_k\right)\right)\right) \\
\qquad\qquad + \log\left(\prod\limits_{k=1}^K \frac{\Gamma\left(\hat{\mathcal{S}}_k^i+\alpha_k\right)}{\Gamma\left(\alpha_k\right)}\right)\right)
\end{aligned}
\end{equation}
I don't want to use &+ because then it gets aligned with the equal signs, and I want it indented a bit further.