[tevake]

I've got a suggestion for you. try swimming with a mask and snorkel. No fins, for most its the breathing that lets them down. Its hard to get enough air at the right time while swimming freestyle. But with the mask and snorkel you can keep your head down so your body stays in a good position parallel with the surface gliding well thru the water.
It can help to vary the pace. Slow and easy most of the time. then kick it in at the end.

It's good to swim breast stroke if you just want to cruise along and not fight for a breath or tire yourself too much.
Challenging to get back into swimming after a long time away, But stay at it and you will see big results in short order.

Cheers Richard