cycle all over the place - on minipill

have taken the minipill previously and had no issues - in fact even since Samuel's birth have had no issues until recently.

History
Since Sams birth been taking minipill and cycle once returning in November was 30and 32 days respectively
Since January have had a cycle of 20 days and 21 days respectivley but have only gone for 3 days each time
In this time I have not been as regular with the pill as I should be and BF has reduced to 4 feeds during the day. Could this be the reason for the funny cycles???

Now adding to this - since my LMP started 17 Feb (again only 3 days long) we last DTD 23 Feb (i'd missed the pill a bit the following week due ten million other things happening) and now for the last 3 days (Cycle days 15 onwards) I've had sporadic cramping and am now feeling sick in the gut (possibly nerves) and have really bloated up (eg 1.5kg in a week)- if and when I get period pain it is usually just the day before AF starts so don't know whats happening.

Anyone got any advice

Sorry this is all over the place but I'm just not sure why my cycles are suddenly all over the place, whether I should be concerned (not really the right word as I'd be more than happy) that I might be pregnant (and thus should be changing my lifestyle to suit), or whats going on.

Any insight to this jumbled mess would be appreciated.