Feeling weak

Damn I hate being ill, I started training again on Monday but i felt really weak and tired so i took it really easy. I went out on my bike for what felt like the first time in weeks, i rode for about 1hr15 at a comfortable pace. I did have to do a few mins at absolute max pace as i was being chased by 2 big black dogs, which really frightened me. What is it with me and dogs lately? i am actually getting scared of going out running or cycling.
Later that evening i did a swim session, the main set was 4x300m off 4mins but i only did 3.5km then got out, i felt like i was swimming with an elephant on my back!
Tuesday morning I did a 35min run on the treadmill, I started off really easy moving up the pace every few mins until I got into a comfortable stride. Then I had a swim session and although the elephant was still there I did manage the whole session. We did 4.3km which included lots of small distances such as 12x25m, 10x50m, 8x75m, 6x100m followed by 6x150m of drills.
I took my specialized bike to the bike shop for a new chain and retaping of the handlebars so it looks like the cobwebs are coming off the Trek bike if I am going to ride on Wednesday...